Likely, all your spokes have reached their fatigue life IF they are breaking in the elbows. They will continue popping like popcorn, slowly at first and then faster.
IF I were to build a lower cost wheel that I would expect to hold up, I'd use-
A Deore level hub with 36 spokes. (I don't know if you have disc brakes or not)
Sun Rims CR-18. (or Rhino Lite)
Butted spokes.
Sapin Strong 13/14 ga. for the drive side.
A name brand 14/15 ga. double butted for the non drive side.
Brass nipples

Sapim Strong Single Butted Spoke - Wheelbuilder.com
Sapim Race Double Butted Spoke - Wheelbuilder.com

With rim tape, the parts should cost about $120ish and with a proper build, be a long lasting wheel.