Elixirs serve the same purpose as Flasks, but the buff expires if you die. You'll only use these between 1-70, generally speaking, until you can start buying Flasks which persist through death. Try not to die, and carry extras just in case. If you can't find an Elixir with the stat you want, look under scrolls, since they count as battle or guardian buffs as well.
You can try joining a Discord server themed around the class you’re playing, how you like to play World of Warcraft (achievement hunting, dungeon-running, player-versus-player combat, etc.), or your location, to name a few examples. World of Warcraft also has player communities built directly into the game. Find a community themed for newbies, or whatever else you want, and you’ll have a great resource to go to with questions. You might even make a few friends (or fellow adventurers).
XP Potions: The Elixir of Rapid Mind and Elixir of Ancient Knowledge no longer drop. They can be bought on the AH still but are way to expensive for it to be worth it. The Excess Potion of Accelerated learning is available from your garrison quartermaster but only works for level 91 to 99. As of Patch 8.1 you can also buy the 10% XP Potion Draught of Ten Lands.
I highly recommend actually staying in the 20-60 range zones until you ding 62. The reason for this is that despite getting a slight penalty in experience for being over-level, the advantage of having flight will more than offset this. That, and WOTLK and TBC zones are the slowest part of the leveling process. Minimizing your time there as much as possible is worthwhile.
As you can see, both of the guides contain quite the same features. The only exceptions being Dugi Guides does NOT have Gold Guide but it is a slightly cheaper choice. Also when using Dugi Guides, you can choose the difficulty level for the guide; If you want to level up at a faster rate but with higher difficulty, it is an option with Dugi Guides but Zygor Guides does not offer this and instead you will be forced to manually choose higher level guides if you want to skip the guide recommendation.
Mag'har Orc Allied Race Leveling Guide (20-120) Dark Iron Dwarf Allied Race Leveling Guide (20-120) Void Elf Allied Race Leveling Guide (20-120) Best Void Elf Allied Race specs for leveling, efficient zones to level in, and overview of available classes and level 20 starting abilities. Level a Void Elf to 110 for a special set of cosmetic Heritage Armor. Nightborne Allied Race Leveling Guide (20-120) Best Nightborne Allied Race specs for leveling, efficient zones to level in, and overview of available classes and level 20 starting abilities. Level a Nightborne to 110 for a special set of cosmetic Heritage Armor.