I recently leveled from 20 myself. (: There’s an experience buff that starts at 100%(can be disabledat an inn) until 40, then goes down to 75% until cap. (Why 75 specifically? A popular way to level was nerfed and 25% increase was to give everyone a comparable leveling speed)You also get a 300% increase in gokd earned from quests. Yes, it’s massive. Also keep in mind that riding is learned at 40 and requires 50 gold or so. Cheaper with your race’s reputation.
There’s a new type of content available since the third phase that you can use to level as early as 23 which encourages grouping and could probably be fun for you. It has a reputation you can get by doing its repeatable quests, with friendly and honored giving you a great 6p set for each class/spec and some more awesome items later, alongside one rune. It’s also an amazing source of gold. Won’t say more just in case you wouldn’t want to be spoiled on the content itself.
There’s a dungeon from phase two that awards skillbooks that teach you new skills. They don’t take a rune slot. Likely a good idea to do a few dungeons leveling.
Near level cap(which is 50) you’ll have a questline starting at the zone north of ashenvale(excuse me, forgot the name as I’ve never really been there before) that you’ll want to complete.
Speaking of ashenvale, i assume they tried to keep the event relevant.
Also phase 2 added an event at stranglethorn. I can only recommend going for it once you’ve reached level cap though.(This event and pvp ranks can likely get you decent gear as well!)
If you have a profession that can craft gear, you can craft amazing purple items after a secret questline in each phase. Might be worth keeping up with your profession for that reason.
The runes after phase 1 are harder to obtain as they can require more people, defeating strong elites, etc (: i haven’t played a bear but my priest runes sent me all around the world and I’m still barely halfway there finding them all.
There’s also a secret item that can allow you to put a rest area anywhere. If you see people sleeping at random spots and wonder why, that’s it. It should be doable by like lvl 30 if not earlier.
That’s all that came to mind for now at least!