I know its only One position but you could have edited your post to include more. Never played as Ajax but have a look at this shortlist:Raikan007's Wonderkid Shortlist v1 - Downloads - FM-Base - Football Manager 2011 Tactics, Wonderkids & Cheatss for tactics, just play to the teams strengths, good passers then play fluid passing football. Fast players then set a quick tempo and counter attack etc.
I always buy Kara and Marco Verratti before my first season starts. To win the Dutch Lleague, you don't relly need improvements if you use the correct tactics. Try to get as high as possible in the CL (duh) and sell some dead wood. Improve your squad from that point.