Money Making Methods
I'm definetely not an expert on this, but I've seen a few money making methods and can say a few things about them. If you want to flip that will give you lots of money, but please note that I don't know anything about that and for that reason you won't find any tips on how to do it on this site.
I'll list the money making methods with my estimation of the potential maximum, the highest amount I've achieved personally, an estimation of how much you need to invest to get the same amount and a minimum investment for the money making method to be good.
Also my estimate of the potential maximum is what I think this money making method can consistently achieve, meaning you might get lucky and get way more than that sometimes.
PASSIVE
1. Using the Forge
Max: 5m an hour (only in theory for forging divan's drills, 6b investment)
Personal Best: 300k an hour (500k)
Investment: 100k-500k per forge slot thats occupied for basic materials
1-20m per slot for items or advanced materials
It's in the name. Look for forge recipes with a high difference in material cost vs ah price and forge those items.
2. Using Kat
Max: 1m a day
Personal Best: ??
Investment: 10k for any kind of pet, but higher rarity and more expensive pets are preferred
Grab a pet and give it to Kat to increase it's rarity. DO NOT USE KAT FLOWERS! This is supposed to be passive money, so don't invest coins to speed up the process unless you did the math and you still make profit.
If you want to save even more coins, try to level up the pet a bit as every pet level grants a 0.3% reduction of the upgrade cost.
3. Investing
Max: several hundred million or even several billion of coins, but over a long time
Personal Best: roughly 2000% price increase, 36m (got 20 each of harvesting 6 and farming for dummies when they were 100k. I was early game then.)
Investment: any amount of coins, the more you invest the higher the possible return
There's many items you can invest in. Items that are only obtainable once will always be a safe bet (like pet skins or one-time-event items).
You can invest in items that are needed in a recurring event before it begins
You can invest in items that are only obtainable in a recurring event and sell them later when the prices have gone up from their low.
The most risky one would be to invest in an upcoming update by making guesses about which items will have an increased demand and buying those.
ACTIVE
1. Ice Walkers or Goblins
Max: 1m an hour (half decent combat gear and magic find, 5m-20m)
Personal Best: ?
Investment: 100k for some really basic combat gear
You'll get a few Glacite Jewels every hour which go for up to 60k per. Alternatively kill goblins and sell their eggs. Goblins also directly give you a decent amount of coins, so they might be better overall.
2. Farming
Max: 4m an hour (max t3 netherwart hoe, legendary elephant, 35m)
Personal Best: 2.7m in one hour (t2 netherwart hoe and elephant pet, 21m)
Investment: 5m for a decent hoe and a farm
Build a huge farm on your island and farm it using the appropriate tool. Netherwart gives the most profit, but sugar cane, carrots or potatoes are also fine. Since your farming level plays an important role in this, maybe start with a crop that gives lots of farming exp (so specifically not netherwart).
3. Zealot grinding
Max: 10m an hour (precursor eye and legendary enderman pet, 80m)
Personal Best: 4m in one hour, 10m investment
Investment: 2m for good armor and god pot
This is well known, not much to say here
4. Automaton grinding
Max: 9m an hour (sorrow and black cat for max magic find, 60-100m)
Personal Best: 12m in one hour (with higher prices, sorrow and max level black cat, 100m)
Investment: 2m for good armor and god pot
Basically the same as Zealot grinding, but a lot less competitive.
You need hotm 3 for this, then go to the Lost Precursor City in the Precursor Remnants part of the Crystal Hollows and kill the Automatons you find there. They drop Robot parts that sell for 100-400k on the auction house, depending on which one you get. Their drop chance is 2%, so not that low at all. The most expensive part is the Robotron Reflector with a current price of 400k and peaks of 650k in the past. On average the parts are worth about 200k.
Use gear that boosts your magic find.
5. Worm fishing
Max: 14m an hour (mythic submerged legion 5 shark scale, maxed rod of the sea, maxed ammonite pet, 220m)
Personal Best: 12m in one hour (submerged shark scale, maxed rod of the sea, maxed ammonite, 110m)
Investment: 1m for basic fishing armor and rod
You need to be fishing 19 to do this. Simply go to the Precursor Remnants and find a spot with lava. If you found it it's important that it doesn't say Magma Fields when you stand inside of the lava. Once you found such a spot, you're done with the hard part. Now the only thing you need to do is maybe build a little cabin where you can stand facing the lava and have a hole behind you, where your flaming worms land after you fish them.
Use Fish Bait to increase your fishing speed, ammonite, dolphin or flying fish as well as your best fishing rod. Fish for 5 minutes and then kill all the grouped up Flaming Worms.
They have a 20% chance to drop a worm membrane worth up to 100k on the bazaar.
6. Ghost farming
Max: 30m an hour ig (soul whip, emerald blade, billions in your purse)
Personal Best: 9m in one hour (with higher prices, in necron armor, 120m)
7m estimated with my gear at current prices
Investment: 30m (shadow assassin and soul whip)
You can start doing this as soon as you have fishing 26 (to be able to use a soul whip). If you have shadow assassin get a soul whip that explicitly DOESN'T have One For All, as you will need the life steal. Start by running in a circle and hitting as many ghosts at once with your soul whip as you can manage, and don't get too close. You will kill ghosts slowly, but it works.
Use either a legendary Mithril Golem (to significantly boost your stats) or a pet that boosts your magic find. If you feel like you can survive and you do enough damage, swap out your armor for sorrow armor.
Sword swapping works with a soul whip, by sword swapping from a soul whip to emerald blade (if you do enough damage without ofa don't use it, scavenger and looting really matter here) you can onetap ghosts if your gear is good enough.
7. Frag Running
Max: 15m an hour (Necron and Hyperion/other Necron Blade, 1.1b)
Personal Best: 10m in one hour (Necron and Valkyrie + AOTS, 1.2b)
Investment: 120m for Juju and Necron + golden Necron head
Get high tier dungeon gear. A Wither Armor set (Necron or Storm) is pretty much mandatory as you won't survive or deal enough damage otherwise.
For a fast clear a Necron Blade is preferred, but Juju or Terminator work fine as well.
You need a frag bot for this. There's a few different methods to get one.
Ask a friend
If you have a friend that is not Cata 24 yet, ask them to let you party them. Ask them to enable the auto-accept reparty option if they have access to it.
Ask a stranger
Same thing as with a friend, if you don't do it in dungeon hub most people will accept.
Be mean
I'm not gonna promote this kind of behavior, but if you think back to when you played f1 you'll know what this is about.
Get a frag bot from a discord server
Many skyblock discords offer one or multiple frag bots, inform yourself there on how to use them.
Once you've obtained a frag bot (they can continue to play normally if they're a player with a cata level lower than 24), you party them and then join a f7 dungeon. Now simply clear all rooms that have a wither door to get the wither key and then go through the unlocked door until you reach the bloodroom. Kill the giant that spawns inside and then warp out of the dungeon. If you got lucky you'll now have a diamante's handle, which sells for 1.4 - 1.7m.
After that reparty to circumvent the cooldown.
8. Gemstone Mining
Max: 27-30m an hour (max divans armor, divans drill, scatha, 2.7b)
Personal Best: 18m an hour (max divans armor, max titanium drill DR-x655)
Investment: 50m for sorrow and a low tier gemstone drill (very inefficient)
Don't be fooled, to really make lots of coins with Gemstone Mining you need to invest a huge amount of coins as well as time. But once you've done that it certainly pays off.
What you need:
hotm 3 (recommended at least hotm 6, better hotm 7)
Even if you can enter the Crystal Hollows at hotm 3 and you can use Ruby Drill + Sorrow armor + Armadillo to mine before you reach hotm 6, you'll just waste your time if you don't have access to at least the hotm 6 perks, preferably all hotm perks.
Mithril and Gemstone powder
To be efficient you need both of those, if you have below 1m in those don't even start mining.
To get more powder get hotm 6 and level up your treasure finder and mole perk. Then dig out treasure chests in the crystal hollows. You should try to get around 3m Mithril Powder (you won't need much more than 4m) and as much Gemstone Powder as possible.
Get the right gear
While there exists cheap mining gear that allows you to mine gemstones, I'd advise you to skip it. You'll find better money making methods on this list.
Divan armor with 1-3/5 slots unlocked and a Gemstone Gauntlet is the right gear to start with. Later get a Recomb, a Jaderald, the Rock Gemstone reforge stone, unlock more gemstone slots and upgrade the gemstones on your gear.
Improve the right stats
You should prioritize Pristine over Mining Fortune over Mining Speed.
1 Point of Mining Fortune is a 1% chance to get 1 more drop.
1 Point of Pristine is a 1% chance to get 80x drops while mining gemstones.
Mining Speed doesn't do that much, the more you have the less useful it is to get more. Yet it still makes a difference. Don't spend all your powder on Mining Fortune and neglect Mining Speed, at some point paying the higher powder cost for the higher level perk is not worth it any more, if you can level Mining Speed instead.
Mine in the right way
You should always try to mine full blocks instead of panes. The reason for that is, that full blocks give you more base drops and thus allow your pristine to activate more often.
You can either mine in a structure (most popular choice is the Mines of Divan) or try looking for big veins in the Magma Fields and mine them using a Bal pet (the coordinates of veins will be the same in every lobby).
EVENTS
1. Spooky Event
Max: 16m an hour, more with foxy (candied bat person armor, bat pet, eternal hoof, good clearing weapon, 50m/1b if hyperion is the most efficient, which I don't know)
Personal Best: 14m in one hour (candied bat person armor, bat pet, eternal hoof)
Investment: 4m for spooky armor, aotd and bat pet
I'm not sure about the best strategy here.
It's probably a good idea for you to get candied bat person armor and a bat pet, to boost the amount of candy you get from mobs. Also you'll want to get the eternal hoof, as you will make a few million by opening trick or treat chests alone.
Once you have that choose one of the many clearing/aoe weapons. Popular choices are the Juju-Bow (maybe even use explosive arrows), the Flower of Truth, the Frozen Scythe or the AOTD even (ability). With that weapon go to the spiders den and try to kill as many spiders as you can. They will drop lots of candy on death and you'll get to open trick or treat chests containing lots of ectoplasm, pumpkin guts or even the occasional bat person talisman or vampirism 6 book.
If you have a Hyperion or another Necron Blade it might be more efficient to just use a mage set instead. You won't get the candy boost from the Bat Person Armor, but the insane amount of mobs you can kill might outweigh that.
2. Fishing Festival
Max: 9m an hour (recombed submerged legion 5 shark scale, max ammonite, max rod of the sea, black cat for pet luck, 260m)
Personal Best: 13m in one hour (submerged shark scale, max ammonite, max rod of the sea, black cat, 180m)
Investment: 7m for divers, rod of legends, ammonite
When Marina is Mayor there will be a 1h time frame where you can do Spooky Fishing and the Fishing Festival at the same time.
Get the best fishing gear you can afford (Try to get close to 100 sea creature chance by using legion, enrichments, submerged, ...).
Fish using this setup.
When you get a legendary sea creature swap to a magic find set + pet and use that to kill the sea creature (Magic Find doesn't boost the amount of Great White Shark teeth you get, but it increases the odds of finding a Megalodon pet, which you can sell to George for 2.5m).
The same thing applies for the Spooky Fishing
3. Spooky Fishing
Max: 15m an hour(recombed submerged legion 5 shark scale, max ammonite, max rod of the sea, good magic find setup, 300m)
Personal Best: 14m in one hour (submerged shark scale, max ammonite, max rod of the sea, 110m)
Investment: 7m for divers, rod of legends, ammonite
4. Mining Fiesta
Gemstone Mining during the Mining Fiesta, simply doubles your money
5. Mythological Event
Max: 10-20m an hour (leg griffin, daedalus axe, really good combat gear, 1b-2b)
Personal Best: 9m in one hour (leg griffin, good combat gear, 500m)
Investment: 200m for leg griffin, necron and a good weapon (ofa livid at the very least)