We have two or three basic setups. Drilling, "scenarios" empty handed, and "scenarios" with tools.
All of 'em we use mouthpiece, some sort of basic hand protection (lacrosse or somesuch with tools), and something for the groin. For drilling and scenarios, that's the basic setup. One on ones, going for tools, two on ones, assassination style criminal assaults (with and without hustles) etc, just gloves, groin, and mouthpiece. Sometimes we'll use a FIST helmet or some variation.
With tools, the hand protection is a little different. We do a lot of Filipino style stuff, so hand protection has to be a little more intense, we use the aforementioned lacrosse gloves (or similar). We've been experimenting with tons of melon protection (in part because we will work unequal armament and/or unequal initiative), but still haven't found the best solution. Fencing helmets, different types of helmets with cages (steel and plexi), other ideas. Nothing has been perfect in that way because of problems with visibility, air, not enough protection, instability (the piece moves too much when hit), that sort of thing.
We try to use as little gear as possible, being fully aware there's no perfect solutions. The only perfect solution is going to constantly send folk to the hospital, unable to train. Hard enough to keep consistent partners anyway. Essentially, it's up to the person, but we always encourage as little as is safe given the type of contact intended.