Regarding other poster's viewpoints above about my list, I probably went overboard in recommending you a lot of those ones, so maybe just stick to a small handful.
NV base game is great, but honestly, a few mods like Outside Bets (restored cut content) or NPCs Travel (more wandering NPCs in the wastes) only serve to enhance the game even for first time playthroughs. Also, have you downloaded YUP Unofficial Patch for the ultimate bug fix compilation and the 4GB Fallout New Vegas mod? Absolute essentials to ensure the game doesn't crash. I also recommend NVAC, OneTweak, and Performance of the Gods for performance. Outside Bets (heaps of cut content and NPCs restored) Hitman's Animation Resources (changes reloads, sneaking/crippled/jumping animations and more) Hitman's 1st Person Animation Overhaul (YOU NEED THIS) Behaviours (only available at a certain adult modding site, but worth it) Gameplay altering mods I use and recommend:
Other graphics/texture mods I use and like: With NVR 3, expect some more explicit adult/sexual content.
FALLOUT 3 PROJECT NEVADA MOD
There's also custom voice-acting and other mods within the mod (Gomorrah Redesigned, Casa Madrid Redesigned). He also added more gritty realism to the environment/notes/scenarios hinted at in the base game but that were toned back as to not step over the line with certain adult themes (won't spoil it for you, but it's awesome). One of the biggest NPC mod overhauls for the game. The mod author Dracomies went through all of the major NPCs and fixed up any faces/voices that needed sprucing/changes and left all those already perfect. One of the best mods available for New Vegas.