I dont really want to go in depth in what is most effective at the Wikia, so I could use some help here.
My genre i most use is Simulation, Action, and maybe Adventure, and here is my staff:
So which staff should be specialized in AI, Level design, Sound etc.?
Please give me any tips on what I really should focus on training my staff too! I could use it
Well, looking at the training thing, you can see the specializations suggesting that “uh, this guy should do this because he has 450D and 300T and stuff rawr”.
No, not recommended, its Req they use, and that means required.
I just looked it up and none of the staff members is recommended to be anything, it only says the requirement 
Well, the AI guy should be Dennis, Level Design guy should be Stabler, Sound should be Di Margiti and blah blah blah.
…?
You dont seem very helpful, almost like you were forced to answer.
If anyone else have a input/explanation on why and what I should pick, please reply
No one else have any input? Really? 
slow day, maybe 
Generally, I find that it is somewhat easy to figure out specializations based on how my employees stats are stacked. For instance: Nicklas has almost even D/T ratings. As such, he’d be a perfect out-of-the-box candidate for Graphics. James Di Margiti would be best off with AI or Engine as his specialization. Kyle Stabler could easily pick up Level Design if he got 40 more points in Tech. Elias could pick up whichever specialization you don’t choose for James (he’ll need at least 180 design points, however). Trenton could grab Gameplay once his Design hits 720 and his tech hits 180. Finally, Austin Riley could pick either World Design or Sound. Sound seems to be important to Action and Simulation, while World Design seems to be rather unimportant, but I cannot 100% confirm this. As your team stands, you could make great Action games and Simulations, as well as Strategy games, but Adventure and RPG are both genres you couldn’t really take advantage of.
I hope this helps you out!
Okay. Then you don’t need my help then. What i’m trying to say is that the AI, Sound, and Engine needs to be someone with a lot of tech, and the rest are people with more design. If that doesn’t help you don’t ask me again then.