I blitz like hell, so my armies have much smaller native contingents. I have a couple 100% regional armies and the rest of my legions are very much varied. It depends. I basically have no house rules, usually doing what is most effective. I try not to hire too many elites as they make the game easy, but that is about all.

So usually, my armies begin as 70%-90% native, as I train them in Italia. That is especially true for my Marian armies, as the Romans have much better troops then. However, my Armies are large. Usually, a single army consists of one and a half or more often, two full stacks. The first stack is largely native infantry and the second stack has mercenary pike phalanxes, slingers, archers, and cavalry, all of which are better if recruited as far away as possible from Italia (except for the phalanxes of course - they are available in many places). By the end of the campaign, after conquering 10+ territories, I have only about six full Roman units and the rest is Regionals, as they are usually better than any of the mercenaries. The only mercenaries which I always have generals stationed to recruit are the pike phalanxes, Galatian Wild Men, Thracian Peltasts, and Balearics.

As for my regional-only armies, I have two stacks of Cordinau Orcas mixed with Iosatae and Greek Mercenary Generals, which is what I use instead of the mortal heavy cavalry. I also have a stack of Elite Thracian infantry, Galatian Spearmen, Cretan Archers, and more Greek Merc. Generals. Then I have two stacks of Greek Classical Hoplites, with Cretans, Merc. Generals, Galatian Wild Men, and pike phalanxes. Yet another stack of nothing but Scythian Riders and Thracian Auxiliary Cavalry exists. Then I have a Hoplitai and Bosphoran Archer stack, along with yet more Merc. Generals. There is an Eastern stack too, with a whole mix of units, some among of which are Syrian Archers, Hoplitai, Babylonian Heavy Spearmen, and some slingers.

So those are basically all my pure Regional armies. In addition to them I have many more largely Roman or 1/2 Roman armies.

And of course, I am playing Romani, 1.1, M/M, at 221 BC and with 136 territories. Yes, it was quite a blitz, although not as grand as the one by Fluvius Camillus.