Need Economic victory advice

I just had a go at going for an Economic victory on King difficulty, having won my first two games by Domination on Chieftain then Warlord. Unfortunately I started strongly then faded away, finishing 4th. I'm still learning the game and I suspect I may have gone a difficulty step too far too early.

Anyway, I started out building up my first city a bit, built a couple more and had quite a bit of gold coming in because I had my cities by water, and so lots of trade resources. I was researching anything that didn't just give military options, even if it wasn't exactly specific to gold and trade. Of course it was only late in the game that I had the opportunity to reserach Banking, and I'm sure it would have made a big difference if I'd aimed for that from the start.

I ended up building lots of caravans and sending them out, but not getting much money. Then I built a spy, and sent it to a nearby city and stole lots more money than a caraven would ever get. I then tried to send spies to other cities but they were on to me, sending tanks out to block them. I couldn't send spies on boats either because everyone had destroyers and stuff.

So what was I doing wrong? Should I be creating one huge city or a few big ones? Should I be getting populations big early on or concentrate on gold straight away? Are spies the way to go? Should I put a lot into science instead of gold early on to research new techs and get the banking tech?

I also chose to start with a random civilization, in this case the Russians, which probably didn't help. No doubt I should have started with a gold and trade specific civilization.

My short and simple advice would be to not worry about getting gold so much in the early going. Get a few mega gold pumping cities going (with markets and banks and any great people that add to gold that you can find.) On king difficulty, without too much trying, I can usually get over 2000 gold per turn later on, and getting to 20,000 is easy.

Early on I would worry more about science so you can get to banking and whatnot. Just pay attention to how the other civs are going on the "who is winning" screen. If no one seems to be flying to a finish, you can safely proceed.

Ok thanks, I'll do that.