I could write pages and pages of strategy on this. and i will, so just stay tuned to this post as i update it with my strategy for rome.
this is how i play as rome, on emporer.
The very first thing i do is switch my civics to representation, vassalage, caste system, (auto for financial), and paganism. the paganism civic will allow your cities to grow fast as they work the mines and churn out praetorans. have one of your cities build and extra worker, one build about 3 tremes, one build 2-3 galleys, and split the rest evenly between praetorans and trebuchets. As your cities finish the other tasks, set them up to build preatorans and trebuchets too. I'd start researching a great scientist, your gonna place a few in some of your bigger cities for the academy. just keep your wealth afloat, i ususally end with like 20-30% research by the end of hte first war.
I spend the first 16 turns building up a force to attack carthage, setup the tremes and galleys with preatorans and trebuchets, and launch them on all the islands first. you'll probably take a few trips to land all the units and take the cities, but don't worry, we've got plently of time. As soon as you land an adauqate force for each city, work on attacking south against carthage's capital. See the 3 cities on the mainland next to his capital? take all of them and then you can declare peace with him. When you realize that you have enough forces to capture those cities, have all of your cities cancel the trebuchets, and build workers/settlers. You'll want about 5-7 workers and about 7 settlers.
now you should have half of carthage conqured, gained a happyness resource (incense), and now your wealth should be relatively low, thats fine, just keep working it so you don't go greatly negative. i'd do a revolution to remove your state religion now, it helps your diplomatic status with everyone else for a bit. set your research on new praetorans, and leave it there until you get praetoran V (the 9 str, +25% vs mounted one)send all the extra praetorans in italy to the north and east, there is a vast open area that can be setttled very easily, use the praetorans to fog bust and settle wherever you can. I settle all the way to greece (the horse resource to the far east is usually the most SE settler that you can put), and as far north as brennus will let you. All of your cities that you conquered should be building courthouses, theatres, colessums, barracks, and very importantly temples. All the cities in italy should build every building you can, i'd personally start with forges as they'd help build everything else faster. every building is important one way or another, libraries and universities so you can get your new preatorans out, and the temples provide the very cruicial happyness. once you get preatorans you need, set the great person researcher to you can get golden ages to boost your production.
as more money comes in, keep your research up. At this point, it should be about 100-80bc. You can either attack greece or brennus. I'd personally attack greece because they are always powerfull in every game i play, and brennus is a wimp, your preatorans will run over him later. just build a very large force of praetorans and trebuchets, and you'll want about 10 tremes as he usually has a powerful navy. just make sure you set up units on all sides of you because greece is everywhere on this map, so he'll be counter-attacking you from all sides. as war wearyness rises, just tick off the research and start dumping it into culture. because you built theatres and colessums everywhere, you can fesiably have +15 war wearyness and still not be effected by it. Make sure you have a few galleys lined up to take Knosses for the collesus there.
At this point, finish out research on the preatorans. You may want to switch to despotism for the -50% distance to palace and -50% number of cities. You can continue on past greece and take out egpyt, or double back to england and take out brennus. if you try to go back to carthage, make sure those cities that where his were building units for most of hte game, and try to have about 60 or so praetorans down there with 15 trebuchets, as his numedian cavalary and war elephants can do lots of damage to your prats.
just take the victory points, and if you manage to capitulate anyone and you didn't take their capital, you can force them to trade the victory resource to you as the one tribute resource.
