57 is where the rule-substitution question in LG first appears, and is also home to a rather infamous logic game. I'd do that one for sure. The rest of the 50s are, at least in my opinion, rather interchangeable.
Hey @harrismegan Mike Kim and JY have come up with a list of the hardest logic games... you could look that up for reference... also, PT36 and 38 contain two of the toughest games that I'e seen... and then there is the infamous dinosaur game from PT 57.
lol @nicole.hopkins for the win : I actually didn't coz these games (most of them at least) have been mentioned in the various lists in the thread... but here they are: PT 34 Game 4, PT 36 game 3, PT 38 Game 4, PT 40 Game 3, PT 57 Game 3