Just how important are those amazing visuals I see in DCI shows? Stick flips, tosses, and other cool stuff like that. Are they important in making a corp? Will they just teach you like another thing? I'm pretty terrible at stick tricks, and if corps will look at that then I'm pretty screwed.

Corps do not look at visuals when you audition. Visuals are not judged so generally staff do not really care.

Usually the priority list looks something like this:

Good Attitude
Timing
8 on a hand
Accent Tap
Double/Triple Beat Control
Everything fundamental to rudimental drumming
The kitchen sink
Philosophical beliefs regarding Santa and his elves
Visuals

If they want visuals they'll teach them to you. It won't hurt to have a useful vocabulary of visuals. They're fun to learn and fun to do, but accurate timing and 8 on a hand are the priorities of rudimental drumming. Get your fundamentals together first, then worry about Hi Moms and Three Way Backsticking.