Creeper farms are very good late game, I'm pretty sure they sell 2nd best, for 1,000 coins each while magma cream sell for around 1,100 coins each but creepers/gunpowder can be farmed easier. If creepers are too expensive then get porkchop so have pig fall into lava and stuff, slowly work your way up to more and more creeper farms, if it gets to a point where your creeper farm is huge maybe go for a magma cream farm as well just for extra money.
I mostly figured this stuff out with the Youtuber SL4TES, check out his videos they are amazing from him starting with no knowledge of the game to being one of the richest players, so I highly recommend checking him out!
