My advice is to wait until you find something frustrating or keep thinking there should be a better way to do it, then look for an addon which addresses it.

Or look through https://www.esoui.com/addons.php and see if there's anything which appeals to you.

There's huge variation among players in which addons are most useful or important to have and no way to make a definitive list because it depends on what and how you play. A casual player who focuses on open-world content, crafting and housing, a PvP player and a member of a hardcore trial progression guild would need very different addons and could all waste a lot of time and effort installing and setting up all the addons each other use, only to never use 2/3 of them.