The earliest you'll be able to get Jovic is 01/01/06 (or at least it was for me) as he's only 16 and doesn't even have a full cap yet. I've got him on a pre-contract but no idea how good he can become. Contract expires 2018 but if you are very quick, this might be an extension from start - don't know to be honest, I only signed him in 1st January window.
He's @ Red Star Belgrade in case you're looking for him and will cost you about £300k & 2 Milky Ways and a Curly Wurly a week in wages.
It's random up to a point but Avdijaj has suck seriously sucky mental stats in my current save: Concentration, leadership, teamwork all 7's, work rate 9, positioning 5. Physical isn't much better: jumping reach 5, stamina 8, strength 6.
Going to have to go with Richpage13, £ for £ (pun completely intended) you need Carlos Fierro in your life.