Walkthrough tips, Discussion of Campaigns [Heroes 5]

The thing is, Vlad catches up to me even in the Dungeon; he has such good logistics that you can’t escape him. I’ll have to replay. I played on Recruit a while ago, and now I’m trying on Veteran. But how can I quickly level up the summoning spells, like “Summon Phoenix” or “Summon Elementals”?