the scenario is what the promoter - and you - make of it.
Scenarios are generally mission based...so the more missions completed, the more points are awarded towards a win.
You need portable water because the games are generally 7 or more hours long. Any 3L [100oz] hydration bladder will do.
With your particular set up, envision your "paint to gas" ratio. A 20oz tank gets approx 1100 shots per fill on most HP/blowback markers...so carrying 2500 balls is simply a waste of energy and resources [unless you carry a 2nd bottle in your pack].
Wear COMFY footwear...something you can be in for HOURS.
If it's your first at that field, try to get a 'field walk' before the game starts.
Every scenario has a different set of rules. KNOW THE RULES [OF THAT GAME] BEFORE GOING. This helps eliminate 'issues' on the field when you get there.
Radios are cool but pretty much a waste of time...unless you HAVE to keep in contact with someone [command].
Bore your paint to your barrel properly and then take along the next size up. Sometime later when the paint warms up it will swell. Having the next-larger barrel/insert will help reduce barrel breaks for you.
Headwear is important...either in the form of a DU rag or BB cap and depending on your location on the field...have clear and smoked lenses available. Inside the treelines, use clear or gradient. Out in the open, used tinted or mirrored.
A vest is nicer than a pack because it distributes the weight of your gear over your whole body...not just on the small of your back. A remote line [regardless of marker] is a good idea as well.