Right now they're in party cups but they're pretty close to outgrowing that... what size pot should I put them in? I wanna go ahead and put them in the "final" pot so I don't have to transplant again... I've heard 10 gallons. Is that good?
Then go with the ten gallon pot if you want to go straight to the final size, but it can be a bit of a pain to get the water and nutes right for a small plant in a big pot.
You might consider peat pots. The ones I use start to disintegrate around the time they are ready to be transplanted, I cut a few slats down the side, and transplant the whole pot. Keeping seedlings in large pots was much more difficult than pots more appropriately sized.