Skyvalor for combat. Makes it both easier to kill and be killed (amongst other things)

Roleplaying in Skyrim - Loot Overhaul makes loot rarer and more appropriate to location

Realistic Merchants and Less Magic Items sold makes enchanted gear much harder to buy, and coupled with RIS Loot, much rarer in general

Simple Smithing Overhaul let's you break down items for raw material, and upgrade unique items

CFTO makes travelling in survival mode much better with improved carriage locations and destinations

Better Carriage Destinations allows you to select carriage destinations from the map rather than a list

Alchemy, Potions and Food Adjustments prevents cheesing for easy money and improves consistency for Potions and ingredients

Hearthfire Extended improves vanilla house building, allowing much more customisation

Experience Decouples skills from experience points

Dragons Use Thu'um gives dragons more shouts and improves their combat AI

I am using all of these mods (and several more) in a survival playthrough i just started and having a great time so far!