I always go for dual roles if possible on most players except for say around 4 players that are specialists in a particular position like DC,MC or ST of which those 3 positions your going to need, I like my wing players to be AMR/MR and AML/ML so I can push up or back if I need to and also like DC/DMC as well so I can play a V formation or a standard flat formation like 4-4-2 or 3-5-2, just a shame that the game doesn't generate players like MC/AMC or AMC/ST often or they could be useful. I also like DC/DL or DC/DR or even DL/DC/DR so I can switch between 3N,3W and a flat 4 at the back (I never play 5 at the back).