In order to save up gold quickly, you must be mindful of your character’s professions. According to various sources, the most profitable profession back in the day used to be herbalism. Mining and skinning are right up there as well. Gathering-oriented professions have an advantage compared to the crafting ones in the early levels because gathering doesn’t require you to spend gold in order to make some coins. You can find plenty of herbs to collect, ores to mine and beasts to skin, all while you’re levelling. Everything you manage to gather can then be sold in the auction house fairly quickly.
An advice for those who are trying to compete monopolizers: you cannot beat them by selling for less if they follow right steps. You should do opposite: sell for more. Because market will come down if the price goes unreasonably high. You can set a bid on item for the price it should cost and buy out price for higher than a monopolizer is selling. So, common buyer may get an item for the right price or monopolizer has to buy the item at his loss.