I think you will find any and all answers to be personal preferences, but here are mine.
Most “half shell” helmets made for MTB are ok, I prefer one that has MIPS or some other rotational system. If it fits, and feels comfortable then great. Think about ventilation, especially if you sweat a lot.
As far as knee and shin pads, they can be great. I find them to be very hot (I do sweat a lot) so I find that I usually only wear them on really tough trails or ones I’m unfamiliar with.
Same for elbow pads
Gloves: In the summer I usually opt for thin gloves like those from handup gloves simply again because I sweat a lot. They aren’t padded on the knuckle areas but do a good job; but all other seasons, I use glove like Fox Dirtpaw gloves because catching a knuckle, on overhanging brush or branches isn’t fun.