I need to get a couple files for some light gun smithing but I’m not sure what to get sizes and tpi.

I need a round one to relieve my G10 grips for ease of reaching the mag release on my CZ ams some various flat files to use to blend the mag well.

Brownells has a good selection of gunsmith specific files. As for G10, sandpaper wrapped around a wood dowel works much better than a file for shaping. Fine files just clog on G10.

Be sure to use respiratory protection and good ventilation when filing/sanding G-10, since it's fiberglass. Also, Ken @ Hogue recommended rubbing sanded G-10 with a little oil to help treat it.

In addition to a nice half round file and bastard file, 2 of my favorite are a fine flat pillar file with safe edges....and a triangle file with 2 safe edges.

EZ-laps are great to have as well and some diamond files.

Don't cheap out too much on files, there really is a difference

 
Chalking your files (especially flat edged files) keeps iron particles from embedding in the teeth, which will mar your work. Chalk them before and during use. Brownells sells "file chalk", which is nothing more than regular blackboard chalk in bigger sticks. It's cheap insurance.