Just recently I got back into Skyrim after spending along time out of the game (due to a poor choice in Mods) after reinstalling the game and doing the traditional hunt for cool mods to improve the base game and now using the new
Nexus Mod Manager making it far easier to implement the mods that I wanted.
Here is a short list of mods that I feel improved my game play.
Immersive Armors V5 (some nice armour for players and NPCs)
Expanded Towns and Cites {Expands the towns and Cites making them look more realistic}
SkyUI {Improves the UI alot}
ApachiiHair {adds more hair options for your characters}
Racemenu {Improves the race menu UI}
Amazing follower tweaks {Improves the way followers are handled in the game}
Better Blacksmithing {adds a whole lot of stuff you can craft}
The eyes of beauty {adds more eye colours to choose from}
Immersive Weapons {Adds more weapons to the game}
Alternate Start - live another life {Allows you to choose where you start off your adventures}
I have many more but allot of them are to improve the look of the game and can kill compies that aren't up to it.