Here's some advice that's been posted in a few other places - and some of my own advice
Use collectors for armor/weapons instead of going and buying when/if you can. This will save you money as well as materials in which later you can use for you guessed it - more money.
Metal = iron/steel and this can be a hefty market as well - made 2k on some iron i had collecting dust in my mats section.
Buying skills whilst in Prophecies - do this very very seldom - you can get a lot of nice skills whilst just doing quests.
Be frugal - after a while it just seems to build up. You don't always need to have the most leet of something when... the weapon you have is max (for your level etc). Once you have the money get the weapon that you've been eyeballing for a while, but not until then.
If you have Factions - Make a pvp character and AB for which ever Faction you're on. Turn the faction into jadeite/amber and sell it either on the market or to a rare mats trader.
Set goals for yourself - This means in nicer terms... Put yourself on an allowance. You won't spend a penny until you reach a certain amount, and only then, it's a small amount that you'll spend.
