Instructions
Save, Save, Save!
Instead of upgrading your gear every level, try upgrading every 5-10 levels. This will put you a little behind your peers in the equipment department, but considerably ahead in the money department.
Roll as much as possible! When in an instance (Dungeon) or just questing, so long as your Guild rules allow it, try to roll for every piece of equipment possible. Even if you can't use it, you can sell it!
The Auction Hall is your friend! The Auction Hall is by far the preferred way to unload gear you don't want.
Quest! If you prefer to simply level-grind, perhaps you should look at the odd quest. Most quests give a fair amount of money for their completion, often with an item reward. While not always useful, the items they give can always be sold to vendors!
Take two gathering professions instead of a gathering and production profession if you want to REALLY save money. This not only allows you to make money from two sets of gathered materials, it also frees you from having to use any materials to produce goods. In most cases, the materials (ore, herbs, raw fish, cloth, leather) sell for more than the goods that are made from them.
Find crafters! Many item-crafting players (blacksmiths, enchanters, tailors, leatherworkers) hang out in the capital cities and offer to make items for free if the materials are provided. This will save you LOTS of money since the items they can create get a nice price markup in the Auction Hall!
Quest solo. This can get you more money and more experience than playing in a group, but it is also much more dangerous. Only do this if you are confident in your abilities and the area you are fighting in.