You could just not infuse everything. I have almost 200 cores and over 15 weapons I masterworked myself. Stop infusing the same weapon over and over every time you get a higher light item and you won’t run out. Problem solved. You don’t even need to run the highest light gear you get, as long as you have equipped the highest light items you had at least once, you should be fine. The game drops items based off your highest possible light, not your current light level.