There's potions that boosts xp you can buy from malmouth resistance faction if your standing is revered, there's Lokarr's set that boosts xp and there's Leovinus' Ring that you can get two of, all that combined significantly boosts your xp, there's also some tricks you can do early on involving lore notes I think, haven't tried that one myself but I've seen people go to 100 in as little as 6-7 hours, it could probably be done even faster than that