Make sure you actively search for your own players, rather than leaving your scouts to do all the work (as they are inadequate, most of the time). If you set the filter to whatever you're looking for, and load leagues like Scotland and Wales, then you will find some real gems! Just make sure you aren't spending too much!
Also, make sure your tactic makes sense, I find that a 5-3-2 works (three centre backs, two wing backs, a holding midfielder, two centre midfielders and two strikers). If your tactics are sensible, then it will most likely work (for example, if you don't play a 2-1-7 or two poachers). I would suggest making keeping it simple, making the defenders just normal defenders, having a Ball Winning Midfield and an Advanced Playmaker, and up top having a Target Man; Poacher combination!