Start with the 5 essentials "C's" of survival:
-Cutting tool = Mora Knife
-Combustion = Fire Steel
-Container = Widemouth metal bottle & metal cup
-Cordage = 200' Paracord & 1000' of bank line
-Cover = Any type of Tarp, Tent, shelter...
Those are the essential non-replaceable items... beyond that it depends on your individual needs and situation. Flashlight, compass, fishing equip, food, water purification, first aid, bandana, fuel, ammo, spare glasses, etc...