Depends what team you are and what you are challenging for.
4 recommendations i can make from the SPL that actually are pretty decent and can cut it in game at EPL level are that i have tired and tested.
Celtics: Emilio Izaguirre-Age:25-Value 2.4 Million-Mid Epl team
Rangers: Lee Wallace-Age:24-Value 900k-Level-Mid/low Epl team
Ranger: Sasa Papac-Age:31-Value 750-Level-Mid/low Epl team
Dundee United: Barry Douglas-Age 21-Level-Low Epl team