Pretty much any paintball field will require paintball goggles. JT's are great for that...and their thermal lenses help with fogging. The facemask is detachable...so you can take that off and run just the goggles if you'd like that. Some guys cut the facemask part down to help with aiming/shouldering weapons.
Other games are played where they require full seal ballistic eyepro...but it doesn't have to be paintball goggles. So glasses like WileyX, Oakleys, ESS, etc...are commonly used. PB Goggles are fine though...and plenty go with those.
Mesh masks are becoming really popular. Either full "wraps" that go ear to ear...down to just a "cup" that covers lips/teeth. Lots of guys use a shemagh and bring it up when they expect engagements (field games, not CQB).
Skirmish games are typically 20-40min "quick games". You don't necessarily need to carry supplies, water, food while in-play. Breaks are frequent...
Milsims usually have you "deploy to the field" with everything you'll need for the duration. They can be most-of-a-day to 30+ hrs. In those cases you'll want to sort yourself out for the activity. Doesn't mean you need to carry it all the time...it's common to stash your stuff somewhere in play and go back to resupply/respawn...but it won't be close to the car
Canteens/nalgenes...hydration packs...they're all common things. Lots of options where you run it in your rig...or keep it in a pack. I prefer to have a bottle on me...and a hydration pack in my backpack.
Hope that helps.