Sachys: I've been wanting to mod it for a while (primarily for new content like you mentioned), but have NO idea where to start - I find both the steam workshop thing and nexus mods to be a right mess.
I suggest you stick with NMM (Nexus Mod Manager) it will make your experience easier, I remember when I started modding Fallout 3 years ago, almost everything was manual, headaches headaches.
I'll leave you this guide series, this guy is awesome, I learned everything I know about modding Bethesda products from him, this is a begginers guide exclusively for Skyrim, he's a slow paced fella, but it's actually quite good at teaching.
https://www.youtube.com/watch?v=RxQ1JN_X-_Y For more content I recommend you to get Immersive Creatures, Immersive Armors, Immersive Weapons, and a island called Falskaar, totally lore friendly mods mate, don't worry.
Also, if you get stuck at some point, or you experience any issues I'm always available to help
Note: For better results make sure you're in the right mood for modding your game, otherwise you might get bored or fuck something up. :)
Edit: You can skip part 4 and 5 (I did, enhancement over graphics is my style) should you want it.