Lighting!
Source is a bit more de-saturated and I would make it so the shadows are a bit less darker. You should also turn the specular and diffuse to 0 if they aren't already.

It is not a good game and I would rather remake or keep it private. :P

No way you got them leashed up

For better scalability, I would use an in-game currency and track what they buy. Comes with its own issues as well.

u can use the micro profiler + roblox's script performance thingy... i generally just check how fast code runs