I'm planning for entering Div III:
13,500 Bleacher
2,500 lower
500 court
40 luxury
I see no reason to limit production of bleacher until you hit Div III or 13,500. This is because once you hit around 13,5 you need to decide whether to build more bleach or more lower.
13,5 is a good number because you can hit pricing of $13 each when you get the bonus seating by winning a title.
2,500 lower is a nice round number to begin Div 3 with. I'll be adding around 1,500 before I move to Div 2.
500 court is good. You can build 500 court in Div 4 without selling out at the lowest price.
40 lux is max for Div III to sell out all seats.