Something I've heard too, is that they tend to come in fewer numbers if there aren't as many troops around the areas they usually appear (always Khazar, sometimes another territory or two nearby). I'm not certain that's accurate, and if not someone can correct me, but you may actually be better off leaving Georgia without any troops, keeping your huge counter armies back in Trebizond or Armenia the turn or so before they arrive and then move back to defend Georgia the next year. You may be able to avoid going to war with them immediately, too. Anyway, have fun!

Lot's of good archers, preferably xbows if you can make them yet for their horse archers and to soften up the others, the best spears that you've got for their heavy cavalry, and the best heavy cavalry you've got for their foot soldiers. I've yet to master Ghazi tactics but if you've got them figured out they could help a lot. I'll assume you haven't teched anywhere up to where you can build Janissaries what with your military vs. tech problems. Pity.