I agree it is expensive to bribe enemy families, but one thing I found was actually fairly productive was to bribe both the smaller armies of other factions and, better still, the bandits in Italy. I am playing as the Julii, and I was able to acquire about 3 or 4 town watch units, plus some velites, by bribing bandits in Italy, and all very cheap -- less than the production cost, I think. I also found that if Rome, the Scipii or the Brutii sent out only two or three units I could bribe them, adding to my own forces and taking away from my foes.

As a general matter I've really been too impatient to build up a solid economic base. Instead I build up huge armies, then leave them in forts on the border with Rome until I am ready, then -- strike!

Fun.

As for phalanxes, I find the entire trick is to hit them from behind (it also works for german spearmen, and similar formations). Move some cavalry ways out to the side, then run them behind the enemy line. This works well if you have more cavalry than the enemy (you don't need too much more). Then hit the phalanx from the front (even if it is just with missiles) and then have the cavalry charge the rear. It will break.

It is also amazing what you can do, sometimes, on sheer willpower. I once had a VERY understrength unit of 1 hastati and 1 velites (each was about 50% or below, they had the plague) attacked by an egyptian general and another unit of chariot archers. The little board thing was like totally red. I took personal command on the field, and I managed to kill the general and rout the egyptians.

Boy was I surprised.