I'm level 1, so just starting out. I manage to get full 200/200 stadium at $6 but at $7 it drops so keeping it at $6 for the time being. Capacity is currently being upgraded by 400 so I'll get 600 max capacity. Won't be able to fill that for a while but we'll see

Ultimately, it's a question on whether you want more money or more possession. At $6 I get 5% possession and $1.2k per home game (ignoring merchandise). At $7 dollars I got 3% possession but $1.25k. This isn't much more money overall because the stadium is small so for the time being I'm prioritising possession bonus until I can generate more income, then I'll see what happens.