I think we can go round by round, simply pick the winners of each game in that round and whoever gets the most right wins that round. We could start with say 100 credits to put up to play round 1, everyone puts up 100 credits, picks their winners and the winner takes all, then round 2 can go up to 200 to buy in, winner take all and so on...
Tie breakers can be determined by the total score of a particular game, closest wins the tie breaker for that round.
Or we can set up a group bracket challenge and everyone can fill a bracket out, say like 250 credits per bracket filled out, pay outs can be determined on how many people we have get in. It could be winner takes all or 2nd gets their 250 back and winner gets the rest or whatever