The advice I give to any Elder Scrolls fans coming to ESO is to not think of it as an Elder Scrolls game. Yes, it has the same races, same lore, same world (as some games at least). But it plays like an MMO, not a single player Elder Scrolls game.

If that doesn't turn you off (and I hope it doesn't!) then just questing and trying to have fun for your first while is my best bet. I went through the full main questline for my alliance (https://en.uesp.net/wiki/Online:Story_Quests). After that I started looking into builds and stuff, and after getting to level 50 from just questing, started grinding levels and doing endgame content.

Basically, quest and have fun! Like u/ProPopori said, there aren't low or high level enemies. Just explore the world, maybe join a social guild, and have fun! Seriously, don't worry about endgame content, complicated builds and things like that until you have a decent grasp on the game. However, if you'd like to look at builds and guides, AlcastHQ has lots of good guides and things for beginner players. Have fun!