My advice is to figure out which decade you want,, and that helps you figure out what shape you're looking for.
Do you like the 50s? Then you're looking for a no crown guards submariner or maybe an early explorer, or GMT.
If you like the 60s, then you're looking for submariners with crownguards, like the 5512 or 5513, or maybe even an early GMT with square guards.
When you reach the 70s or 80s, then you're starting to look at early sea dwellers, more submariners, and getting into the transition model subs.
From the 50s up through the late 70s and early 80s you're looking at plexiglass crystals, then the transition models of subs ushered in flat sapphire crystals.
That's a high altitude perspective, but it might help you narrow it down.