Diving right into ripping 3d models (which would include textures and likely animations as well) is going to be a rather steep learning curve, even more so if this is some unknown game on a console or something compared to a PC game using a known format.
That said textures without 3d models is not pointless (you could edit the texture while knowing what the result will look like in your head as it were* and import that back into the base game you ripped it from) but limiting enough that whatever guide you were learning from the rip textures should include some basics on 3d models as well.
*you were effectively doing a variation on this when you made the 2d texture resemble some projection of the 3d model by yourself/your imagination. Texture wrapping if you wanted a search for there, and indeed texture unwrapping as well.