1. Click this link and download the "fpsboost.cfg". () 2. Open your "common/garrysmod/garrysmod/cfg" folder and place the "fpsboost.cfg" in the folder. 3. Start garrys mod and at the start screen (Note: Not while in a server or you will crash) open your console and type the command "exec fpsboost" then hit enter. 4. It will load your screen may go black for a second or two, once done close your console join a server and enjoy the fps boost.
Note: You need to do this everytime you start gmod. Note 2: This will hurt your graphics but not much and to be honest I almost like the look better, things will seem a little bit more pixalated and players will have no eye balls but hey you cant complain if you are getting 30 or less frames and desprately need to increase your frames.