Not sure it's worth buying someone in just for free kicks, seems incredibly hard to score them in this version...can you not train wilshere or Ramsey as they're both pretty young? Corner taking on the other hand seems to provide quite a few goals...
I'd guess the most important attributes would be free kicks, technique, long shots and finishing in that order? Try giovinco or Honda, had a quick look and they seem to have the right attributes mate!
I am Arsenal and I brought Honda in for free (For the merchandising in Asia and to sell him on again) been a really good backup and has scored 3 times from free-kicks (Baring in mind Cazorla is my main freekick taker)
So definatly try to get him, although I doubt he'll go into the starting XI for most games (Depends on your formation)
EDIT: Oh yeah, and I got offered £18m for him from Real Madrid, so good bit of business financially even if you don't want to play him