Facilities don't have any big relation with tanking.
My team ALEXANDROSS, even if it's staying for 25 seasons in the 1st level, I keep building my facilities (when I gather some money or remember to do it).
Now my stadium (and the other stuff) is LV4, with 13.000 seats when the 1st lv has 200 seats.
But there is also a max number of attendance for every lv.
For LV1 it's 800 fans.
Today in my Cup game, I had full fans (800) in a stadium of 13.000 seats but still got the 5% tickets bonus.
Hope it makes sense
Normally, if you keep building, your full stadium can be completed at LV16.
You can read that thread about levels
https://forum.topeleven.com/top-elev...prices%5D.html