If you’re looking to create new unit skins, a good place to start is by picking an existing texture and working on top of it, as someone already mentioned. It’s one of the simpler ways to get a feel for how skins work. Once you get the hang of it, you can dive into custom meshes and actors. For some inspiration, you might want to check out what's available on https://skin.land/market/csgo/ak-47/ . Seeing how skins are designed there could give you some ideas on creating your own.