Army composition question

[BobMaster]

Yea, obviously

Still learning myself, started this because I finished all the HoMM games and VI wasn't out back then.

But this access to all races thing really adds a huge difficulty, at least for me, thank some deity it are the same units though

Let's hope some expert KB player can help some regarding magic use

[EDIT]: After searching some more on the forums, I realized I possibly screwed myself by maxing higher magic too early, mass or even lvl 2 blind and stuff would have been more useful.
Will try to pick my fights carefully and hope I can advance, or I need to restart ... again