The most important step in being able to buy a mount and make other large purchases should be self-evident: saving. Economize as often as you can, and don't buy anything unless you absolutely have to. You can burn through hundreds of gold even before level 20 by visiting the auction house for new equipment at every opportunity. If you do so, over the long haul you will be left with very little to show for it. Before level 20, keep your eyes on the prize: getting that mount. The mount helps you move faster. Faster movement means faster killing, faster questing, faster quest turn-ins, and faster leveling. It is the most important tool to fast leveling you can get at level 20, and infinitely more important than getting your hands on that Left-Handed Vorpal Cleaver of the Zipswitch that you could have purchased at level 23. Stay focused.
There’s a mountain of endgame content in Battle for Azeroth, and looking at it from the bottom can be pretty daunting. Between the variety of extra quests and their rewards, gearing up for the game’s hardest dungeons, most competitive PvP or even the first raid can be a tall task. Thankfully, we’re here with a helpful checklist of overall goals in the first few weeks, as well as things to do in the days and weeks after you hit 120 in Battle for Azeroth.
The leveling experience for the Burning Crusade and Wrath of the Lich King levels of 60 to 80 has been greatly reduced from 6,689,030 XP to 4,412,600 XP which is a reduction of 34%. This has been a notoriously lengthy leveling section, and this reduction will be very noticeable and appreciated by those players leveling new characters such as those allied races!
2. Begging - Many guides will tell you begging is worthless and will not work because people get agitated. This is not entirely true if executed properly. As more players accumulate gold through Wrath and Cataclysm items and professions, the number of casual players with gold obviously increases. These casual players remember how it was to just start off and be poor. They will often donate a few gold to a sob story or a "noobie". Look for the players that are not in full epic sets of the best gear, but rather, the ones in heroic gear or worse.
The most simple thing is TradeSkillMaster. This AddOn shows you quite an amount of information in the items tooltip. In my opinion, DBRegionMarketAvg the best source. It tells me the price, an item was posted on all EU realms in the last 14 days. Why not DBMarket? DBMarket only shows you the items value from your server in the last 14 days. This value often gets manipulated. Some people start to post an item with a 500g value for 500.000 Gold on the auction house for several weaks. As a consequence, DBMarket is rising towards 500.000 Gold.  If you use DBMarket with 100% and post your item for 500.000 Gold, nobody will buy it.