Easy peasy with drones. Just build on of each type in all four corners first off so you have 4 of each type (upgraded obviously), then spam upgraded upgraded boosters wherever you can have them touching a hero. The final upgrade for drones makes their money on death bonus double so therefore, even if they die in mass they are still keeping the bullets off of you, doing damage, raking in the cash and since there are 4 of each type, the diverse spawn times usually leave you well protected. I'll find myself with 3k all of a sudden since I'm mostly paying attention to teleporting to avoid that minigun. Once that happens I just spam mines all over the place to stun the heroes as they get destroyed by both my gun and the drones. Pretty easy after you get a few stars. You really only need 24 stars to become overpowered. Well, that's how I played it at least.
Just killed a dragon with mid/high weapon and high armour and jsut and elixer! :P Immediately after with barely any health, guess what appeares? Another dragon... D: I have never gone from happy to sad as quickly as that moment... :(
 "Realm Grinder"){kind=icon}
 "Monster Saga"){kind=icon}
 "Kill the Heroes"){kind=icon}
 "Trigger Knight"){kind=icon}