you don't have a optimal distribution of seats, because the seats are affected differently by the succes of the team.
The amount of VIP Boxes sold, is nearly independent from team succes, and mostly affected by tradition(how long you play) and league level.
On the other hand, the bleachers and lower TIE are highly affected from succes, so that a succesful team can sell there seats for a higher price there.
This difference leads to different strategies to build your arena, a succesful team maybe get his money invested in the Arena earlier back when he build lower tie and bleacher seats, while a unsuccesful one better invest in the VIP Area and the courtside at this moment.
And also the flexible price decision, could give you several options to build the arena, and getting nearly the same amount of cash ;)
So when you have figured out a good arena pricing, look at your team and try to calculate how many homegames you need, to get the building money back normally the area where this happens fastest would be the best for "small" investment. If you increase your arena big times, i would check team with your level of your succes in the division level who already have such a big arena.