What should I upgrade next? I'm leaning toward my Stadium.

Current level:
Stadium - 6
Training complex - 8
Youth center - 7

In my opinion, it's always good to upgrade the stadium as soon as possible (the 80% pretty much makes it likely that your additional profit will soon overtake additional maintenances costs).

Otherwise, youth center 8 is a pretty big deal. After that, youth center 9 isn't really worthwhile except as a stepping stone to youth center 10 (the maximum potential of players doesn't really rise with youth center 9, just the minimum potential). The training complex is cheaper to upgrade at that point and affects all of your pre-existing players.

Yeah, I would upgrade stadium then fanshop if you are hitting 80%, then hit youth 8, then training 9 and 10.

What's bumming me out is I could upgrade right now but I couldn't watch some of my recent matches. It's a killer seeing the attendance, knowing that if I could have watched the match I would have gotten the 80%.

Then go for YC. Get your 2 extra men at the start of the new season.

I've never been able to log on in time often enough to upgrade my stadium sooner. In any case, the increased maintenance costs might make it better to wait until you can hit 80% in most matches against sufficiently popular teams anyway. If you think it will take a while to be able to upgrade the stadium (though the stadium would be more important if you are close), then I would in that case second Avy Nguyen's suggestion.

According to my calculation, stadium should always be in a priority list. Until you are planning to build a level 8 stadium, this building is not only tremendous overpriced but also expensive to maintain...You probably won't profit at least for two seasons. Anyone has different calculated result, please tell me... Right now, I just finish a level 10 training complex and heading for a level 9 youth...