What are the player roles of your players and what kind of philosophy are you playing. ie. Direct or short passing ?
As a continuation of this, I'll give you my view.
Incidentally I must make it clear that I haven't played with any of the above players since the good old FM11 Lukaku days, but I doubt I'll be too far off.
Mitrovic, Lukaku and Lewandowski are more than capable of playing as a lone striker. They're either strong enough to pin themselves on a central defender and (especially in Lewandowski's case) technically good enough to either hold the ball up to bring inside forwards or attacking midfielders into the game.
In my opinion, Mitrovic and Lukaku play best with wingers who stretch the play, get in behind the defence and put crosses into the box. If this is the route you want to go down, any sort of direct, high tempo 4-3-3 will do well for you. A 4-4-2 should also be able to do the trick although I haven't really used one to any great level in FM14.
As for player roles, you can't really go wrong with an Advanced Forward; they'll do everything you expect of a striker and most likely score you a hat-full of goals. In theory, the Lewstinater should be able to work well as a Complete Forward but you'll have to just try that and decide for yourself.
With regards to Jese, I'd play him as an Inside Forward with Lewandowski as a False Nine, perhaps even Lukaku as the right IF (think Everton's recent win over Arsenal). If you're ever playing with Inside Forwards though, remember that due to their natural movement in towards the centre of the pitch, any player in the number 10 position will most likely get crowded out, create congestion in the centre and ultimately reduce the effectiveness of everyone involved.
Good luck and remember to watch your matches, see what's happening, try to understand why it's happening and make changes accordingly.