So I think I can simplify a lot of Gun's stuff into simple terms. 

Gates - basic level stuff, stuff that's the base for everything he does. 

Genesis - makes stuff 

Integration - combines stuff 

Distortion - breaks down stuff, but also can be used to apply force

Eversion - destroys stuff

Induction - applies on-hit effects to stuff

Repulsion - mimics stuff

Gunsmoke - makes stuff decay faster than normal

Electric Light - absorbs energy and stuff

White Album - A very fancy gun that can modify other guns

Riotbreaker - Another very fancy gun that can make melee forms