Hi, and I think you will love Skyrim! There are so many mods, and you're going to get a lot of answers, not all the same. I'll make some suggestions. The first will be to read and get the USLEEP, or Unofficial Skyrim Legenday Edition Patch. This is almost essential, it fixes huge amounts of bugs, fixes and restores cut content. The team that does this is very very good, and you'll find that many mods will rely on this. It supports the main game and all the DLCs. TES5edit and LOOT are the second essentials, you probably already know about them.
SKSE, Skyrim Script Extender is practically a must
SkyUI is a menu replace and so much more, is awesome, and allows access to an MCM, Mod Config Manager (in game to tweak certain mods)
Cutting Room Floor by Arthmoor, restores even more cut content. He also is the primary for USLEEP.
RaceMenu, gotta have!
So, that being said, I'll just list a few I use, besides the above:
#1, I don't use an ENB, I use Tamriel Reloaded, Climates of Tamriel, (with an additional snow texture) and a load of landscape textures mods that strike my fancy. One mod author that is very very good at landscape texures is renthal311, I have many of his. Browse him in the Nexus and see, he has a lot of individual mods, and some all-in-ones.
The mods I use for females are Dimonized UNP for body type, Real Girls Realistic Body Texture for UNP, Coverwomen, Covereyes, and Sporty sixy Map
The mod I use for for males is Better Males with Younger Faces Merged with Men by Geonox. Many like SkySight Skins.
#2, I don't use a combat mod, though I do have Deadly Dragons ready to activate for another character, along with some other animal mods that make them tougher.
#3 I use UFO, Ultimate Follower Overhaul, but there are a couple other follower Overhauls that are good too. Guard Dialog Overhaul is great, and FCO, Follower Commentary Overhaul.
There are so many great city and town mods that improve the game immensely, JK's city mods are great, and Arthmoor adds villages where there should have been one in the first place but weren't. My favorite city is Whiterun, and I use Perfect Whiterun to make it even better.
All of these are on the Skyrim Nexus and are easy to browse for. One of the best things to do is browse using the 'Most' Endorsed' filter, and you'll see what I mean. Another author to browse is Chesko, great mods.
For realism and immersion: Frostfall, Realistic Needs and Diseases, Hunterborn, and Campfire.
All of these are just the tip of the iceberg, and all on Nexus. LOL Like I said, you're going to have many opinions, you'll have a lot to look at and decide on. Have fun and have a stable game with learning and research! Enjoy!