In the World of Warcaft there are the usual haves and have nots. Unlike the real world, being a "have" in WoW isn't all that hard. Not at all. Note, this isn't "skill," this is just acquisition. Now, if you have skill and acquisition skills, well then, you'll rule the game. Imagine playing in the mid level battlegrounds and you have all the best gear that you can beg, borrow, buy, or steal.
So let's talk about gear. Everyone wants to have the best gear at all times. It's not necessary, unless you're in a competitive game (such as PvP or raiding,) but it's nice to have and provides certain bragging rights.
The worst way to get geared is by diong the ingame quests. You'll get a certain amount of gold, rep with some faction, loot from the monsters, and some decent green items from the quest rewards. It'll keep you in Ok shape for questing, but bragging rights? Nope.
Now, if you work just a bit on your gathering skills (mining, herbalism, skinning, pick two) while leveling you will be able to earn enough gold to make regular stops to the auction house to buy better gear. It'll all be "green" gear, but it'll be a big step up from quest gear and will help you level faster.
The nest step up is the dungeons. Everyone thinks of the hot gear that you can earn from Heroics or Raids, but all the dungeons will provide better gear then anything you'll see from questing or Auction House camping (unless youi're rich.) It's somewhat hit and miss though. You'll have to get lucky. Maybe the boss drops the right gear and maybe you will win the roll to get that piece. Eventually you'll get some good stuff. In addition to the dungeon loot, you'll also get a "sack of useful items" which will always have a piece of nice gear, though you might already have that piece.
PvP, if you like that game, is a very good way to get some nice gear. As you level you will collect "honor points" from the Battlegrounds that you participate in. These points can be spent on the gear of your choice, which removes some of the randomness from things.
At the high end of the game (level 85) you can do dungeons for Justice Points, Heroic dungeons for Valor points, PvP for honor points, rated PvP for Conquest points and you can use all of those points to "buy" nice gear.
Then there's some pretty nice stuff on the Auction House. Those pretty Epic items that cost thousands of gold each. Maybe it's time now to talk about the wallet fattening part. Buying those epic items, or even paying for repairs, consumables, miscellanous stuff, equipping your alts, is going to cost. A lot. Care to spend some time earning the cash to pay for it all? If you're not then I hope you have a rich friend or generous guild. If you don't have those resources then put in a bit of effort into earning some WoW gold and you'll be able to buy your mounts, repairs, and some nice stuff.
The easiest way to start is to gather and loot stuff. Pick any two of the gathering skills: Herbalism, Skinning, or Mining. Next, find an area with creatures that drop something worthwhile, such as wool cloth (humanoid mobs in the mid 20s) or skins. Set aside an hour and kill everything in the area while gathering all the ore or herbs in the same area. After the hour is up, or your bags are full, you post all the good stuff to the Auction House. It's helpful to have an alt to send it to, then you can log into the alt and take care of the selling chores when you have the time.
If you're high level you can clean out lower level dungeons by yourself. You get to keep everything and you can vendor the junk and send the better stuff to your alt to sell later.
Daily quests at high level pay nicely and provide rep with some faction, guild rep, and sometimes also points that can be spent on items. The quests in Tol Barad are a good example of this. If you get a good routine going with the dailies then you can earn a decent amount in a short time.
All of the crafting professions have items that sell well, and for a lot more than you will spend to make those items. Which items is the trick and varies daya to day and from server to server. You will need to study the Auction House to learn that and you will find that the Auctionator and the Tycoon gold addon will be a big help. These two will let you analyze your server's auction house and discover what's selling.
Take a look at some of the items you can create and see what they sell for on the AH. For example, the dress shirts and clothes created by the tailoring skill can sell for shockingly high amounts. They don't necessarily sell fast, but if you can corner the market you might do well. Items with useful stats will always sell. If you can find a spot in the market for your items then go for it.
Sometimes items are priced very high, such as some glyphs, for example. Try putting yours up for slightly less than the going price and you might do well. A lot of people in this game have a lot of gold, they might as well send it to you by buying your stuff.
If some doofus posts a bunch of stuff at a very low price, and you know it will sell for a lot more, then buy up all of the cheap stuff and sell it, not all at once, at the higher price. Let's say you know an item that you can craft sells well at 100 gold and Bob just posted ten at 2g each. (Yes, it happens all the time.) Buy them all up and post them one or two at a time at the higher price.
Getting a fatter wallet in WoW isn't hard, at all, but you do have to be willing to spend some time to do it. Pull yourself away from leveling that new alt and spend a bit of time doing the stuff that will earn you some gold. Keep that up for a few days and you will see some good results. Work it hard and you'll be able to buy those pretty epics with petty cash. There's a reason that Blizzard raised the gold cap from 214k to a million; it's because some people are doing the work to earn it. Why not you?