If you feel confident you are going to win your league and promote, don't buy anyone this season. You should be able to get some cheap deals on some older people at the start of next season when everyone else is looking for young trainees. Wait until you see what your league looks like before you decide how much to spend on players and your arena as some divisions are much tougher than others. Plus you get 200k for promoting. You will probably lose the first 2-3 games until you have an advantage in gameshape (if you know you are going to lose, tie for the enthusiasm) then you can start to pull out some wins.
Most importantly, try to make some money. You want to make atleast 60k a week for a while so you can keep doing the upgrades to your arena and roster.
Lastly, you need to improve your perimeter d. Do whatever it takes. 2-3 zone won't get you very far against a decent div 4 team. It can be effective, but at minimum you want to put up an average(low) rating.
good luck!