0.30 or 0.40mm for a first proper piece?

I keep seeing gauge numbers all over maker sites and I want to actually understand what I am choosing. For a first fitted piece, say a simple top, is 0.30mm going to feel too flimsy, or is it perfectly fine and I am overthinking this? I like the idea of a lighter feel, but not if it means I put a hole in it within a month. On the flip side, does 0.40mm get stiff or extra hot? I am not chasing the heaviest rubber going, I just want something that survives a beginner and still feels good. What do you actually reach for day to day?