1) most of the time, being an early war monger is not a good idea. This is more true on BnW than it was in earlier versions. This is precisely because you will end up skipping infrastructure for units, and that puts you behind.
You DO want to build 4 "bows" early as they are the best defensive unit. if you tech towards x-bow after the NC, then early x-bow is an awesome offensive unit as well, but you need some swords to protect them.
Get an early NC.
2) If your going to play wide, you probably want to start with Liberty policies. This can be very different from Tradition. You should plant new cities whenever you have the happiness to spare, and a unit to garrison. 6 cities max. 5 might be better. Its not hard. You MUST have a source of happiness, you will need to build shrines and monuments early. Get happiness from religion if possible, plant cities next to lux and connect them asap. At the end of liberty, get a Great engineer and use him to build a choice wonder, thats what I like to do.
3) Navy: this can be a long-haul investment. Play on Archipeligo to feel it out. Epic game pace to have more time with each set of units. Build galeas upgrade-> Frigates. These units *MUST* get promoted to range +1 in the long run. Frigates with range +1 can sit outside the City defenses and bombard until the city can be captured in a single attack by a caravel. You can get the XP for promotion by DoW-ing a Ai (or CS) and just grind the Galleas / frigates there (dont capture the city!). Make this close to friendly territory so you can retreat and heal quickly. Once you have all promoted to range +1 you should be able to capture any city, without taking a hit!
the only thing that can stop those frigates now is another navy

so bring some Privateers along as well. The Frigates will upgrade to battleships, with range +1. enjoy
Also, the privateers can be promoted in a similar fashion. Pick a city just outside your territory and send one privateer at a time to attack, then next turn retreat to heal in friendly territory, and send in another privateer. Dont capture the city. Pick a city without a ranged unit in it. Get the promotion that allows attacking twice in one turn. Once you have that, you can hit & run.
During this whole affair you will be gettign +20 GPT, which is nice. You need ~6 Privateeers to keep the cycle going.
Combined with the 5 frigates with range +1, your navy is unstopable.
(until submarines)
then you need destroyers
etc.