I suggest playing on the lowest difficulty, go for peaceful mode (this will curb the AI's tech advance and let you hang around longer in eras to get your expansionist stars). Play on a smaller map and if possible pick Harrapans, Egyptians, Assyrians or Olmecs first (basically the cultures that are generally good at generating influence in the ancient era, arguably the hardest era to do this since influence gain is difficult and you can't get the land rights civic that early)). Then race to claim as many outposts as possible, because the AI are on peaceful they won't fight you over territory unless you start the fights. Try to get as many luxuries as possible, even trade for them since you'll be getting alot of territory

, you'll want as much stability as possible.

After that, odds are you'll be behind the AI for every culture pick, so just pick things you like I guess (although the Classic Persians are good for securing more land, because generally smaller cities are easier to build up rather than stacking as many territories)). Until you get the land rights civic and gold income to buy territories, cities, etc with gold instead of influence its going to be expensive to make more cities. However a trick is to surround an outpost with a reasonably strong army, liberate it (requires and the independent AI will eventually turn it into a city for you (that should default be high enough to be a peace with you) which you can just steam roll with the army you have around it, thus circumnavigating the increasing new city cost.

You will also want to buy out as many independent peoples as possible to claim their land (if its too many cities, you can always ransack the city and build an outpost on it and claim in the neighbouring city)

I have basically all the achievements besides the two bugged ones (Landstalker and Wonder-full) so if you need any tips on the other ones I can help.

EDIT: Also forgot, I found playing a slower pace game, gave more time to get territories. Also you will need to do this in one sitting currently (no save loading) otherwise it won't count the stars (its a bug).