If you know nothing else about Simpsons, probably the best shot is the center/garage. It starts modes up top, leads to multi and the feed to the right flipper is safe. With limited time before the tournament, I would try to learn a basic stack around that shot.

In your warmup time, I would focus on the games you know reasonably well and not the games you don't know. No amount of warmup on unfamiliar games will make a win likely. Also, there's nothing more soul-crushing than wiping out on a game you know really well.

The scoring also comes into play. If the tourney uses a papa style scoring of 4-2-1-0, then what you want is FIRST! If you suck at simpsons and spend all your time warming up on it, maybe you go from 4th to 3rd as a result. One whole point. Likewise, because you didn't warm up on Addam's Family, which you know really well, you took 2nd instead of first. You gained one point but lost 2.