Buy a 5* MR and a 5* ST but do it now, today You say that you'll not promote, so it is the best time to buy players. Make sure that they're under 23-25. They'll be helpful next season. Cole will retire, so i recommend you to buy a two-positioned player. DC-DR would be nice. About stadium, build an under-21 facility

Edit : All you need is 3 players i think. Try to get rid of 3* star players as much as you can. They're useless but in level 1, you can also use them. Your choice. Following this advices, you'll probably win the league cup next season.