I would have LOVED to have Infernal at this point, but research on Infernal had just started. Again, the key was having the sand golem in the party for the spiders to expend their ranged attacks (entangle/poison) on. Otherwise, I'm guessing that my Sovereign would have been immobilized early.
A Fire Giant would have worked just as well (and he has a ranged spell), as the spiders like targetting him, but he wasn't online yet...
I had picked up a couple of items that made a 7.1 combat speed a reality sooner than I usually see it. Strength of 18+ is an early priority, to make the bows more effective against armored foes. That and those +1 base attack books/items make longbow equipped Sovereigns almost/as/more powerful than many spells. And no mana cost to boot.
I would have also normally had the +2 to attack spell active/slotted by this time, but due to some timing/encounter issues didn't have the 8 mana to spare for it (was about to summon Mr Fire Giant once the TOE came online in a couple of turns). That +2 helps out with those bow attacks.
I only boost my Sovereign's mana to a certain point (start at 14, raise IF I don't have 16 mana by the time Fire Giant becomes available). The +1 essence tech is usually one of the first I go for, and once I've grown a city enough, then Temple of Essence comes into play. I find that some stuff in the later game doubles/triples the mana total, so all I have to do is wait... Again, I've found that strong Sovereigns with bows and some attack bonuses are pretty scary at range, hence combat speed being a priority for stat gains (allows more ranged attacks/turn). I try to save mana for area attacks once they become available, and for summoning, if possible.
Besides, the kids generally have LOTS of mana, so I let them be the spellcasting geniuses, and have my Sovereign do the heavy lifting.
A quick note, I am playing on 'normal' difficulty, and 'fast' turns as opposed to normal or epic, should anyone wish to know.