FPS booster is it needed?

I dont think youll need it gmod is fine as long as you have 60+ fps

Search about multi-core rendering on Google. You can usually double your FPS. There are also addons on the Garry's Mod workshop that do it for you so you don't need to type commands into console every time you start the game up.

you didnt need it you know gmod is like a bad gtame in background the coding is bad and rly loud

Is you're asking for an Game FPS Booster, and not a Gmod exclusive, Razer Cortex. (If it works for you, lol)