The fief will supply gear, just select it in the equip screen when you're spawning (There will be a limited amount, so some may run out after a few respawns). Essentially after that, you want to keep the flags on the ground under your control (They're little and blue, they're where you spawn), as if all of those are taken over then the enemy wins once you've all died, as you can no longer spawn.
Honestly though with 2000 vs 100, shouldn't need to worry about much. Just kill the enemy until you're out of tickets.
EDIT: Oh one thing I forgot to mention: don't enter the server until about 60 seconds after everyone gets kicked out of the duel server, as if you enter too early your gear can bug out.