As you level, you will buy new ranks of spells. If you splurge out on an item upgrade, you will not have enough gold readily available to upgrade to the latest ranks of spells: placing you behind. Moreover, you can buy gear upgrades from the Auction House (AH) or vendors. Furthermore, you may have large investments that need to be paid for professors. You will need to purchase reagents and items such as leather, bolts of cloth, alchemy supplies – unless you have a charitable friend or another high-level alt.
Step-by-step class guides are on the way! The 1-12 Mulgore Guide is the first guide to get all the individual class steps. At the top of the guide, simply select which class you are playing and the page will dynamically update all the steps in the guide for that class (both text and images). The rest of the guides will be slowly updated overtime to include all the class steps, but you can see how it's going to work with the 1-12 Mulgore. I want to thank crazyK and his Placeholderguild for helping me out with the individual class content. They are allowing me to get the 1-60 Alliance guide done while also getting all the class steps done at the same time, so everything can be ready for Classic launch (hopefully).
Check Item's Vendor Price before posting it on the Auction House - Selling items on the Auction House below their Vendor value is a common mistake. Avoid it like fire, and always make sure that you are not losing Gold on your Auctions. If you plan to sell an item on the AH for a price just a tiny bit higher than its Vendor value, you might be better off just vendoring the said item (this will allow you to avoid the risk of losing an Auction fee if your Item doesn't sell).