Solo/Duo Showdown. Don't play Gem Grab with randoms cuz they might suck and you don't know if you'll win or lose. Its an unpredictable game. unlike in showdown, you can increase your chances of winning by camping etc.
Well if you can get good at brawl ball and gem grab do those they can be pretty short it depends on you’re skill level but when you’re below 1000 do showdowns.solo might be you’re best bet.try ending up in 6 or better.