Vyvyan Basterd
Adventurer
I think the easiest thing is to let the players decide what items they possess, changing every level as desired. Maybe the PC's own power charges them; or they are heirlooms that level with the PC, or the PC's boss/patron gifts them, or they are rewards from a grateful kingdom, etc. For higher level PCs; 1 item level +1, 1 item at level, 1 or maybe 2 items at level -1; and the GM can still give out 'story' items.
This is what I do, sort of. Every time the characters level the players receive a budget of gold equivalent to 1 item level +1, 1 item at level, and 2 items at level -1. They can choose whatever they want and they can describe the acquisition any way they want as long as they don't change the rules. They can describe the item(s) as found, an increase in power in their ancestral weapon, a new technique their character learned, etc. And I still include 'story' items in the form of artifacts in-game.