I goofed around a bit with LA C'tis recently, and I've got a few observations for you. And I agree, having 100% capability for Banefire is pretty sweet.
First thing, as soon as you can afford to, Desert Rangers are awesome. I highly recommend that you actually make them nonstop throughout the game, so you have at least one HInf army around that has map move 2.
Second thing, if you can get to Ench3 fast, groups of 2-3 Sauromancers can skellie spam almost any independent out, finishing out your initial expansion with a bang.
Next, honestly, every single Death gem you can get (remember: search early, search often) should go to Tomb Priests. Personally I think the Kings are a waste, as even though the Wyrms are fairly badass, and Sacred, you only get 1 per turn, whereas Chariots come 2-3 at a time.
Magic Diversity will hurt you a bit, you may well want some sort of Rainbow pretender - but I've no specific recommendations. Things to bear in mind though, you are going to be rather predictable unless you can diversify, and you are unlikly to just be able to have your pretender accomplish everything. So what you really need, is some manual searching on paths you don't start with natively, and to pray for a decent indie mage site that can bring -anything- unexpected to the table. Your Sauromancers are sleek and deadly, and it's not entirely easy to find ways to negate their power - but adding in anything worthwhile to the equation, can tip the scales wildly in C'tis' favor.
Bear in mind, I'm not suggesting that my own strat (do I have one yet, really?
) for them is contingent on finding indie mages, merely that it takes their mid-late game from good to great, if you can find something useful (even Crystal Amazons would be awesome for this purpose, and don't even require the search!).