Why bother unless you buy tokens? 40 or 50 skill points could really make your player better. 50 skill points is almost 1 *.
Free kick, corner kick for forwards, and aerial defender for defenders and 1v1 for GK are my recommendations.
Shadow strikers are rare, so you might want to add that to an AML/AMC/AMR.
Also, I would tend to add SA's to younger players you plan on growing, instead of older players who you will end up replacing anyways.