My limited knowledge of Carthage suggests to me these RP guidelines:

1. Establish a trade empire, not a land empire. Look for hot trade sites eg Emporion and Massillia, and acquire them to build a cats-cradle of trade lanes, not a defensible contiguous blob'o'land. Keep a huge treasury in reserve to show how greedy you are (it'll help with point 3 too).

2. Rule from the centre. FM's like to spend time in the metropolis and major centres, and shuttle around on expensive boats to show off. This should soak up some of the bags of cash that make Carthage a bit of a breeze to play.

3. Mercenaries are your friends. Keep a small elite domestic force at the capital, it can be "loaned" out to adventurous types. Pad the hard core with assorted local mercs when needed, lots of them, and disband when the campaign is done.

4. If you still have too much money establish an elephant patrol on the Ptollie border (liberally supported by elites): keep the incestuous yellow tide in Cyrenaica and have fun doing it. Not even remotely historical but it'll keep the other elements in a bit of balance.

5. Never ever take Rome, until every other VC province is taken. The red devils should be a constant thorn and threat until the moment of victory is reached. I feel Rome always took Carthage more seriiously than Carthage took Rome: aside from Hannibal the Carthies always tried to negotiate and deal with the treacherous Latins like humans and not as a pestilence to be eradicated, to their cost.

I try to vary my campaign by RPing minor allies, thats a local recruited general from a type IV gov, with a local stack (eg a Verrix with celts, or an Italic general with Samnites, brutii etc) carrying on a little local campaign against a neighbouring city or reb stack, or perhaps fending off a major power neighbour until the Punic cavalry arrives by boat. You might do this with Syracuse or Massillia, in fact massillia is one of my favourite "Minors" in the game and I look forward to their mini state expansion into Segesta or the islands (of course my major power has to lend them a boat for that).