Army of Ruin

To be honest, I had no idea how this was possible initially. I assumed that Coin Purse was a necessity as a trinket, but it only increases the money gain from the random coin drops, which are pretty pathetic (worth only around 2 gold each). It doesn't impact money from chests at all, and that's your main source of gold.

So, here's what you should do to guarantee success on this objective and achievement:
 

• First, unlock Favorites (10G) to eliminate the RNG aspect of this
• Buy two of them. Mark Homemade Explosives as a favorite, and Rabbit's Foot as another
• Play as Lanyz, because of the increased Luck
• Upgrade your Interests in the Upgrades menu as high as possible (5+ is solid)

Turns out, Homemade Explosives don't help with this achievement at all, so I have no idea why it's a requirement. They don't give extra money, or higher chance for money drops, or anything like that. Un-evolved, Homemade Explosives are pretty much useless, so you'll want to play to ensure you get the trinkets needed to evolve it, otherwise it's a wasted weapon slot.

The goal in this run is to maximize your Luck, because Luck does two important things:
 

• Increases the likelihood of getting powerups from breakable containers
• Increases the likelihood of getting multiple rewards from a single chest

What we're aiming to do is max out all of our weapons and trinkets as soon as possible, because once they're all maxed and evolved, chests give extra money on top of the existing money. And, when you level up, you get multiple options, one of which is more money, and that's what you'll be picking.

You're going to want to keep decent movement speed because you're going to be traveling around a lot. Get Rabbit's Foot and boost it ASAP, because you'll want as many chests as possible to spawn on the map, and you want as many rewards as possible from each chest. You should also plan to reach and defeat all of the optional bosses for their chests too. The final optional boss always drops a chest with multiple rewards. I have gotten six rewards out of that chest at times. Chests have a chance to spawn on the map at the start of each wave, so as soon as a new wave starts, check your map for any chests, and beeline right to them. If there are no chests, head to the next optional boss. Along the way, always go to every powerup shown on your map, and break all the containers you see along the way. If you're lucky, you'll find a Piggy Bank powerup to suck in coins, and it usually gives 100+ coins per powerup, or you'll find the powerup that sucks in all gems on the map, helping level up faster and max everything faster. Even if you find the Haste powerup, this helps you get to the next optional boss or chest faster, so it's still good.

Remember, you don't need to finish the stage for this achievement, you just need to earn 4000 coins and have Homemade Explosives (or its evolution) in your inventory. On my first attempt with just Coin Purse, I was at 3600 coins and couldn't avoid killing the boss and ending the stage. On my second attempt with Rabbit's Foot, I finished the stage at over 8000 coins. Maximize your Luck, and push for chests and bosses.