if i were in your shoes, i#d throw all the money i have into my stadium, so i can have a good regular income later on. but, if you really feel the urge to build something right now, i'd go with the fitness center, cuz it's the most useful facility for teams with little income. fitness skills are really important for players, and they don't affect their wages. that's why this would be the smartest way to guy, besides of course building your stadium
hope this helps

stadium stadium stadium