I recommend Son of Black Eye to help learn campaign strat

[bruno]

I haven't finished yet, but I am finding sobe very
interesting. (I am playing on the middle difficulty.)
I am learning the values of various match ups
of Orc units and a different style of campaigning than
used in httt.

I was used to always recalling units in httt. Since most
elvish units are close to 20gp it was reasonable to recall
even level 1 units with some experience and try to
protect everyone. In sobe, this doesn't seem to work.
Buy lots of cheap new units and not worrying who gets
killed and who promotes allows you to press the attack
and finish sooner (and under the deadline).

I am also learning about how to use trolls and orcish
assassins effectively.

I think this will help me when I go back to Eastern
Invasion, as I will have some new ideas on how I might
do things.

[Attila]

personally I thought that HttT was better to learn the game on. It fits into the tutorial, and it has a nice gradual increase in difficulty.

I did use SotBE to learn wml though.