Also, is this your first con? If so, why not try to cover both of them. You know, have 40% T.T. and 60% Pokemon. (Since more people, I believe, would be Pokemon lovers then Teen Titan lovers. But there are Teen Titan fans out there, including me! Don't have a fav though...) By doing this, you show people that you don't just like one thing.
If you choose 5, then have 2 T.T. and 3 Pokemon. If 10, 4 T.T. and 6 Pokemon. If 15, 6 T.T. and 9 Pokemon. (Yes, I'm good with math)
As for quantity, try choosing a max number and go from there.
For example: 30 (For an example)
5 different drawings X 6 of each one (5X6) 10 different drawings X 3 of each one (10X3) 15 different drawings X 2 of each one (15X2)
I suggest 5X6 or 10X3 if your max was 30. But if your max was higher, I'd go with 10X?.
But in the end, it's your choice! I hope I didn't confuse you...