A few other mods to add in addition to Ink's list.
You want to get "SkyUI", it really improves the older interface and lets you change a bunch of parameters.
Also you'll need the "SKSE" or Skyrim Script Extender, it's not a mod per say but a new launcher that allows Skyrim to use more memory IIRC. The SKSE is needed for many mods to run including some of the ones Ink listed. It's safe and you use it to launch the game instead of steam.
A few more mods I recommend for realism are "Frostfall - Hypothermia & Camping Gear Mod", "Realistic Needs & Diseases", and "Hunterborn".
And as Ink has said you really need to use the NMM, it make's your life so much easier when dealing with cleanup and seeing if there are conflicts. Right now I think I have around 80 mods installed and I rarely have any issues, though you do need to read the descriptions and make sure a mod doesn't conflict with something else. I highly recommend using little to no mods on your first playthru as it'll give you an idea on what you want to install. Just installing a few mods can completely change the game and makes Skyrim highly replayable.
And finally you need to download skimpy armor and sexy skin replacers for Lydia, it's a rite of passage for nerds to roam around Skyrim with Lydia following in her chain-mail bikini.
