Winning 30 games of Caravan in Fallout New Vegas is pretty easy, despite how rare the achievement for it is. The easiest way to do it is to just farm Ringo for wins, but you can use any NPC that plays Caravan. Alternatively, you can just play Caravan naturally as you progress through the game. You might not get to that 30 number, but it'll get you close enough that cleaning up at the end of your playthrough won't be too tricky.