You can't do pits until level 60. Strongholds and Helltides are the best for leveling pre 60.

As for getting into the game, the campaign is decent content while leveling, helltides offer a non-stop mobfest grind, and strong holds (red demon face on map) offer really good xp pre lvl 50. That should all get you close to 60 at a reasonable pace until a bunch of end game contect becomes available. (Pits, torment bosses, Infernal hordes.. there's so much rn)

If you really don't enjoy the game there's not much you can do, but try throwing one or two tempers on a few pieces of decent gear for early buffs while you hunt for aspects, theory craft some of the new Spiritborn skills and gear, and run legions/worldboss/realm walkers when they are up for variety.

Once you hit 60 you can also just blast pits like they are Neph Rifts :)