Hard to analyze without more details or some screenshots of what you're doing, but in terms of general advice, I'd suggest looking through the Help/Civlopedia and running your eye down the index real quick. If there's a whole section that looks unfamiliar, or you're not sure what to do with it, like religion or trade, try focusing on implementing that in your current game.
There are certain strategies that people seem to generally use (some civs, social policies, and wonders are seen as far better investments than others), but just following what others do takes a lot of fun out of having a personal playstyle, not to mention can be inefficient if you don't understand the reasoning behind those strats.
Still, if I had to suggest a basic mode of play for the lower difficulties:
Build about four cities
Focus social policies (SPs) on Tradition, Patronage, and Rationalism
Keep research somewhat balanced, try to get most of the techs in an era before moving to the next. When you start a new era, focus on getting the ones that boost research (let you build things like Libraries and Universities) first
Stick the guilds (Art, Music, and Writing) one each in your non-capital cities, keeping your capital (it's usually your best city) with fewer specialists so it has higher production for wonders
Stay friends with your AI neighbors, and experiment with bribing them to go to war with one another. Really important strategy to understand on higher difficulties.
As far as a civ goes, Arabia does everything decently well, their unique building gives craploads of money, and their UU is neither too early nor too late to be relevant. Poland's unique ability is so generalized as to be helpful regardless of what you do, and doesn't require you to focus on it in any way.