If possible, avoid purchasing Gear from the Auction House - Ideally, you should be able to achieve level 60 without buying anything from the Auction House. This way you will save Gold, but possibly make leveling a bit harder for yourself. If you badly require an Item upgrade, and the suitable Item is available on the Auction House for a low enough price - buy it, but only if you think that the investment will pay for itself in one way or another (the main exceptions to the Auction House ban Rule are Weapons and Wands, as they make leveling much faster, and pay for themselves by allowing you to chain-kill more mobs without Eating and Drinking, which saves Gold and time).
Learn only the Essential Skills - Learning new and upgraded Skills gets very expensive very quickly (Buying a single skill that requires level 30 will cost you 1 Gold, and a single level 40 Skill costs 2 Gold) If you buy just the essentials, you can save anywhere from 15 to 30 gold before level 40, depending on your Class. Generally, higher ranks of skills that are used for their utility effects can be skipped (these include Warrior's Harmstring, Rogue's Gouge and Kick, Mage's Frost Nova, and many other CC and utility skills and abilities). Also, don't buy any ranks of abilities that you will not use during leveling (things like Rogue's Expose Armor, Hunter's Eyes of the Beast, Warlock's Eye of Kilrogg, and so on).
Whelgar's Excavation Site - This Dwarven excavation site was overrun by Raptors (Mottled Scythemaws and Mottled Razormaws). These reptiles are a great source of Medium Leather (you should have Skinning Profession if you want to farm here, as a very large portion of income that comes from this spot is acquired by Skinning Raptors). They also drop some Vendor Trash Items and Raptor Eggs (these are convenient, as a Cooking Recipe for them comes from a Quest that is located just above the Site) that can be used for Leveling up Cooking Skill. However, the best part about this spot is that both Raptor types present here drop level 19 Twink Gear (Feet of the Lynx, Sentry Cloak, Redbeard Crest, and Twisted Chanter's Staff) that will achieve astronomical prices at the later stages of the Game (drop rates are very low, so some RNG is involved, sadly). Recommended Level - 25+.