U must add more troops since the drones are killed to easily. And here's an idea: maybe u shouldnt do it with a system of credits but with a system of time, so the more powerful the troop more time will take until u can used it again!
README file: "What is one important asset to an invasion? A dropship! Invade any UNMERGED map with this script: Dropship.lua! (It won't work properly if the map is merged. If you really want to invade an merged map, you can split it using Atque). You can deploy up to 2 different types of units, which you can order to attack any enemy by 'shooting' the enemy monster (make sure you have fists out). NOTE: Your units can be distracted before they fire at their given target A dropship is also supposed to be able to fly. Press the "previous weapon" and "next weapon" buttons (for those I use Q and E since I control with WASD) to adjust the speed to reverse or forward (given in the upper left-hand corner) and the microphone button to activate the thrusters (recommended to set the caps lock key as the microphone button). Thrusters: when you have thrusters on, you are capable of flying around as you please, but you cannot use the cannon. When you have thrusters off, you are air-braked and cannot move anywhere, but you can operate the cannon and your health will charge up. NOTE: you will always know when you have the cannon as your current weapon if the weapons HUD is blank. you cannon switch from it (for whatever reason) until you activate thrusters again. To select which unit to deploy, press the toggle map button. The unit that is currently able to be deployed (by pressing the action button) is indicated on the top middle of the screen. To recall your units, press the alt-fire button. NOTE: once again, your units can be distracted by enemies before they get to you. The current cost for Hunter-Seekers is 500 credits, and 525 for the Drone Brute. You gain credits by killing enemies or from your units killing them. You cannot have more than 5000 credits. All in all, the credit system will be a bit choppy until I can figure how to fix it better.