It really depends on what you’re looking for.

You have basic bug fix/patch mods - Unofficial Skyrim Special Edition Patch, Unofficial Skyrim Creation Club Patches, Scrambled Bugs, SSE Engine Fixes, PO3’s Tweaks, etc.

They’re all great, and I recommend at least checking out the mod pages for all of them to see if they interest you.

“SkyUI” is a necessity for most of us on pc. It overhauls the UI to be a lot more usable, and is a requirement for loads of other mods.

You also have overhauls - I recommend checking out the mod authors Enaisiaion, and Simonmagus616. Both have mods that change the game in different ways, with Enai aiming for more of a power fantasy, and Simon going for more of a VanillaPlus feel.

If you’re more interested in Enai’s approach, check out his mod page and be sure to grab “Ordinator”. If you’re more into Simon’s approach, go ahead and grab his mod “adamant”, which also requires his other mod “mysticism”. Adamant overhauls the perks, while mysticism overhauls the magic system. From there you can explore their pages and grab whatever mods interest you.

Lastly, there are some massive dlc sized mods you might be interested in, that showcase the peak of what modding is able to achieve imo. All of which, imo, rival even Bethesda’s own content.

• Legacy of the Dragonborn - adds a massive museum to display all of your unique items, has a full quest line where you travel to different provinces, and is incredibly well voice acted.

• Beyond Skyrim Bruma - This mod adds Bruma and it’s surrounding area to the game. It’s incredibly well made while also being incredibly well voice acted, and even comes with tons of different quests.

• Forgotten City - This mod was so good it was literally remade as it’s own fully made game. I don’t want to spoil much but the story and mechanics are top notch.

Sirenroot Deluge of Deceit - Smaller than the others, but one of the most unique quest mods on the Nexus. I don’t want to spoil much here either, but I recommend checking out the mod page.

Let me know if you have any questions! I know this was a lot.