First of all do an author search for "Arthmoor" and download the unofficial patches, one for the base game and then one for each DLC you own. While you're there it's worth taking a look at the rest of his mod list, "Run For Your Lives" (and "When Vampires Attack" if you're running dawnguard) is pretty much essential and "Cutting Room Floor" might interest you.
After the patches it's really up to you. What do you want from your game? Want to add to realism? Frostfall or a needs mod might be what you are looking for. Planning on playing as a Mage in your next playthrough? Then have a look through the spell mods, too many to name and some pretty cool stuff to see. Got a monster of a PC and want to push the graphics? ENB's, SMIM, and hi res texture packs will be right up your alley. For map extensions, there are a few new lands mods with Falskaar and Legacy of the Dragonborn being the big boys.
It's also a good idea to search for GopherVids on YouTube and watch his beginners guide tutorial series, it covers stuff like load order and mod cleaning
- Hypno