[Evilhomer]

Those 3 buildings cost money as well, that can be better spent on more troops. More troops will allow you to expand faster, which gives more gold (due to more lands) allowing you to expand even more.... In short you don't want to add all buildings everywhere, especially early (exception might be late game ermor since they cannot build troops/mages but thats another story).

I generally spend all my gold on troops/mages until the point I hit an income of 1500+, at that point I add a fortress+lab in a strategic or good province.

As to strong EA nations, you might want to consider a bless nation (strong sacred unit that your priest can cast bless on to give them bonuses related to the magic path of your pretender).

For example consider Niefelheim, and pick an cyclops and chose the alternative imprissoned for him to get more points. Then increase his magic to 9 i earth and 9 in nature. Pick a dominion score of 5 and order 3, cold 3 and the rest as you can afford or want. In each battle bring nifelgiants (big guys that cost 150 gold) and use a priest with the script to bless those guys in the beginning of the fight.

If you really don't want to play with a bless, consider a nation that has elephants/mammoth. A good such nation is Caelum. Build lots of mammoth as you can afford and mix them with other units that has high morale (in the same group that is). Research offensive spells like thunderstrike and orb lightning for your mages to use (Eagle kings are good offensive mages).