Well, you'll probably get some cash for the friendly, and more cash for any season bonus, plus cash from your new Sponsor.... If you only have 1 Stadium section open - you might want to wait until getting all this cash to dump into that section.

I'm hoping to have 300k in the bank after this stuff.... then I'll use that to purchase as many Trainers as I can... then buy all the seating I can. upgrading one of the trainer areas to 15 would cost 71k in bonus + 23000 per week in Wages... to get the Trainers I need 10x Wages... so 230k+70k = a bit over 300k, of which I only actually spend 71k - leaving 230k to dump into the stadium.

With 250k I can get 10 trainers and do the same thing... so that's my plan, just waiting on Wed to see how much I have (plus that way I'll get the training benefit before Paying a week's Wage).