Just follow the quest line at your current level. Play battlegrounds and queue for random dungeons. There's no definitive way to level in WoW, although there's certain quests that you can follow in certain orders to get to level 85 faster
But what if BY CHANCE you lose all 5 of your first matches that put you into a rating? So you end up at an extremely low ELO. But perhaps you're a better player than that and you just got unlucky on all 5 matches, or you was having a bad day etc.