None of these suggestions are for SE because I don't use SE. Any or all of them might require SKSE and SkyUI. Looks like you're already using the only good mod manager (MO), so that's good
Bug fixes and essential features:
USLEEP or other Unofficial Patches as needed - you should already have these
OneTweak (requires SKSE) - allows windowed fullscreen.
Vampire Lord drain with Serana Fixed (Dawnguard-only) - fixes the bug where Serana makes your vampire lord drain spell useless.
Kindred Judgement Fix (Dawnguard-only) - allows you to complete Kindred Judgement as a vampire.
ShowRaceMenu Precache Killer - prevents the race menu from precaching hairs. Necessary if you have a lot of hair mods.
A Quality World Map and Solstheim Map - With Roads - adds roads to the map so you can tell where the hell you're going.
Optional:
Better Xbox 360 Controller - 8 hotkeys quicksave/load - the vanilla controller support includes only TWO hotkey positions. This changes the buttons so you have eight of them (using the left bumper as a modifier, making select open the hotkeys menu, and making left bumper + select open wait). This also adds a screenshot shortcut to the controller (left bumper + start) and auto walk (left bumper + press right stick). I play with a controller and I have no idea what I'd do without this, but if you don't, you can probably skip it.
FNIS PCEA2 - like PCEA but less of a pain. You can use this to replace player animations without having to run a utility all of the time. Needed for the next mod.
Spears by Soolie - FNIS PCEA2 Version - gives you spears in Skyrim without making you rip your hair out like the old version did.
XP32 Maximum Skeleton Extended - you might already have this since it's required by basically everything, but as a note, you can use this to put spears on your back.
The Joy of Perspective - use if you need to see your character in first person mode to feel IMMERSED in this game where NPCs ragdoll a million miles into the air when a giant hits them
Start As Series - Female Breton - I got really fucking tired of the race menu defaulting to male nord :/
Elys's Uncapper - use to make the crafting skills not a slog mainly. If you use the SPERG perk replacer, it recommends that you gain perks every other level instead of every level, so it's also useful for that.
SPERG - Skyrim Perk Enhancements and Rebalanced Gameplay - replaces the vanilla perk trees with vanilla-like automatic scaling perk trees. If you don't use Ordinator or PerMa or whatever, this is a really good mod to pick up.
Enhanced Blood Textures - i'm vile
Acquisitive Soul Gems Multithreaded - fixes soul gems so that lesser souls stop polluting your grand soul gems.
Apocalypse Spells - adds new spells that make being a mage actually feel powerful.
Bound Weapon Redux - adds more bound weapon spells, since the vanilla choices are kind of pathetic.
Knock -An Open Lock Spell - in older TES games, you could open locks using Alteration spells. This adds a spell that does that and automatically scales based on your Alteration level.
Paralysis Disarm and Knockdown Immunity Enchantments - I got a mod that adds irritating paralysis effects to certain enemies that results in stunlocks. This adds enchantments you can use to block that.
Field Alchemy - in older TES games, you could carry around alchemy equipment instead of having to find an alchemy table. This adds a mortar and pestle item you can use on the road.
Armor/clothing: thought i had more of these but here are the ones I have installed right now
Practical Female Armors - replaces most of the female armors in Skyrim with non-stupid armor.
Adventurer's OutfitCloaks of SkyrimLustmord Vampire Armor - mildly questionable but looks cool enough that i don't care
R18Pn 01 - Eisen Platte Armor - if you want to be a final fantasy or whatever
R18Pn 02 - Leere Armor - if you want to be a ragnarok online or whatever
R18Pn 04 - Ritter Armor - if you want to be a tactics ogre or whatever
R18pn 09 - Shanoa Armor - if you want to be Shanoa, and I mean, why wouldn't you
Armor mods that aren't on Nexus:
VS Trek Wear Dress and VS Medieval Archeress Dress WARNING: LOVERSLAB LINK. Not an adult mod, but taken down from Nexus.
VS Noble Archeress Dress WARNING: LOVERSLAB LINK. Not an adult mod, but again, taken down from Nexus.
dint - Nier Automata 1.5 english version WARNING: LOVERSLAB LINK. If you want to be 2B or A2. Looks better than any of the alternatives I've seen. Not an adult mod, but the author doesn't allow their mods to be put on Nexus. Requires
Heel Sounds (ALSO LOVERSLAB) and
HDT HighHeels (Nexus). Also requires a non-disgusting HDT preset file.
Other:
No one cares about Nazeem - Immersion mod.