So, I've been playing CIV for a while now, finally able to beat Noble on an almost certain basis. My question is, how much gold does everyone keep on hand and why? I used to run as little as possible until about the Middle Ages, and then start building it up once I got rifling so I could upgrade units. Then I liked to keep it around $2000. That was when I spent more time with Universal Sufferage and paying to complete things if I needed to. Now that I've discovered other civics I don't use Universal Suffage much, so I've got some extra gold lying around. I recently played a game where at 70% on the tech slider I was making over 100 gold a turn and at 80% I was losing about 80 (not exact numbers). So I sat there upgrading frigates to destroyers every 5th turn while I made tanks to stomp the remaining civilizations. When I want to upgrade troops it's pretty handy, but other than that, having a big gold account doesn't seem to have much benefit.
What amount do you keep on hand and why?

I generally keep enough to deal with most random events in BTS.

Upgrades, I will adjust the science slider to 0% to get the gold when I need it, or trade a tech for it.

Keeping $2000 gold on hand seams a bit much for my games unless I am very far ahead in tech or just sent a GM off on a mission.

I usually try to keep ~200 for random events. If i can afford it, that is.

I think the most expensive random event i have ever seen needed about 120 Gold to 'buy' the best possible outcome. (That was this terribble dustblow stuff, where you have to pay piles of money to the weather gods, or it will just continue whipping out your farmlands)

Everything but random events is usually planed ahead - like Madscientist said - if you forsee upgrading lots of troops, just drop the science slider to 0 for a couple of turns.

I'll keep a couple of hundred on hand in the early stages of the game to cover random events. I don't really change that until I hit the corporation phase when I'll often keep a few thousand on hand, partly because it's quite easy to turn a profit at 100% science, but also because I can then upgrade and/or buy units wherever necessary in an emergency - like an unexpected AI invasion.

I'm pretty sure the cost on random events changes by level, and the best random events are often the most expensive.

On Emperor level, I once was just a little gold short of getting a free military instructor. It was somewhere around 450 gold.

Aside from gold for random events (you need about 50 in the beginning of the game, and maybe 500 AFAIK by the Industrial age), there is not much point in storing gold unless you intend to use it. And not much point until you intend to use it. If you plan on researching rifling yourself, and then mass upgrading maces to rifles, there is no point saving the money until after you have the tech. If you plan on stealing it on the other hand, and are waiting for a rival to get it, you can plan ahead how much gold you will need to upgrade them all the turn you get it.

I only use <500 gold pretty much throughout the entire game. Once you get into education and beyond, the AI's have enough gold that you can frequently trade a tech every 10 turns or so for ~300 gold, enough to run the slider at 80 or 90% perpetually. About 200 gold spare is all I need, just to run at 70 or 80% at around -15/20 a turn for 10+ turns. For payrushing (I almost never upgrade units) new units or buildings, I'll just crank my slider down to 0.

Uhm, gold disappears very quick for me :(, i just save up if i need for upgrades, else it all goes straight into research and expenses :p

I try to run at 0% or 100% research, so I store up however much gold I need to research my tech. This is especially true if an enemy is going to be able to research it while I have to store up gold, since it gives me a research bonus.

The drawback of accumulating gold is that the AI then tends to ask fo rit.

Depends. If I am racing the AI to a certain tech I will let the treasury run down to 0 if necessary. Ideally, I would like to have enough gold to handle random events though.

Dont forget, that you can lose gold. AI's spies can steal and there is a random event, where you lose 25% of your treasury(great depression I think). So keeping a huge ammount is not a good idea. Just have enough to deal with the random events and drop the slider to 0% research, when you need for upgrades.

I keep about as much as i need to finish the next tech at 100% slider then run it down to 0 then repeat for the next tech etc... If i need to rushbuy or upgrade something you can always just drop the slider...

I like to build up enough to upgrade units. That often requires 5000 or 6000.

one thing I do is when playing a Spiritual civ, I will drop research down to nothing for a turn or two a little more often than I would otherwise and really try to take advantage of upgrade cash from this. I figure since I am not getting any anarchy from civics changes, it all balances out. In a way I think of Spiritual as a great trait for making more money than I otherwise would.

The highest number of gold I ever got was 16,000. I used it later on to finance my war against Persia (formal vassal). Linking India with Egypt

It's not usually a good idea to save gold (or GPs, for that matter) for long periods of time unless you have an important specific use in mind for it. It isn't earning interest or anything, and a fixed amount of gold has a greater marginal impact on the game the earlier it is spent.

I usually keep about 20 gold in the early game, that takes care of the most common bad events, forest fire and slave revolt cost 10 or 11 and destroyed forges (or other buildings 20). Later on it depends on to many factors to give a simple answer..

It's not usually a good idea to save gold (or GPs, for that matter) for long periods of time unless you have an important specific use in mind for it. It isn't earning interest or anything, and a fixed amount of gold has a greater marginal impact on the game the earlier it is spent.

Well I agree with you for the most part. However, there can be an insurance in having a little gold for events. Also, techs get less expensive the more civs that has researched them already. Furthermore, your cities may all have build queues for a long time to come so there might not be an immediate need of obtaining a new tech in the interest of growth at all times.

How much gold is enough?

Just a little bit more.