In general, go for population growth in your starter city in the beginning, try to have a city size of at least 3 before pausing growth to make a worker and I'd usually wait till 5 for a settler. Bigger population = more tiles worked = faster production and growth = bigger popn etc. You'll probably have loads of idle time at the start where there aren't many food or production buildings build science buildings in this period. Build a granary as soon as it's available. Don't bother with wonders at the start.
Once you have got farms, pastures etc researched and your food sorted then get on production buildings and improvements, large pop + high production lets you build and churn out units quicker. Metalworking etc are helpful. Once you have a decent main city with good production and pop, then go for science. Always try to keep your science slider as high as possible.
Also, play as England on the map of earth scenario with 18+ civs, seeing as you start on an island you are pretty safe for quite some time, allowing you to get established with 3 cities (2 on the mainland and one in Eire) that have to be invaded by sea.
Lastly, when attacking an enemy city, bring fucktons of seige weapons, ideally enough to reduce their defences to 0 in 2 turns at most. As well as taking out the defebces, take loads of cheap disposable catapults and attack with them first (not ranged bombardment, actually attack), they'll die but they damage up to 5 other enemy units with each attack, meaning your other units will find it a lot easier going when they attack, it's good for dealing with large enemy armies.
