Im using 0.95mm mild steel ignore the gal, I should not be using it. Makes it alot harder to paint. It's all i could get when i finished work. But on the upside you dont have to worry about any surface rust while fabricating. You can use 0.65mm for smaller panels and if your worried about the weight. I'm not worried about weight thinking I'm past that.
On a small sheet metal bender like the 85$ one im using I would not try to bend anything more than 09.mm.
This is how you bend a simple bend, keep your bends over 40mm, reason being is you have more clamping surface which creates less flex. Nicer bend.
When your working out sizes dont forget to allow for the bend itself, I'm losing 3-4 mm for the bend itself.