In RTR I find the historical approach works best. Move south and kick out the Greeks since they are the biggest threat. Then take the nearby islands from Carthage. Taking any port city will help your economy greatly. Allying with the Illyrians and Gaul early will help with trading while you deal with bigger things.

Then you can move into Gaul or Greece proper once you have a financial base. Swordsmen are great for garrisons but sometimes you can also build cheaper peltast or slinger units in some areas.