Rear wheel has 2 broken spokes. I can buy a set of 40 for $15 on source bmx, so should I replace only the 2 and save the rest or just replace all spokes? More info in caption

It doesn’t hurt to have some spare spokes lying around, just make sure to get the right size(s). Rear hubs often have two different sized spokes.

I’d just replace the broken ones unless you feel like rebuilding your wheel

Best to measure the exact length of spoke in mm to get the ones you need. Each wheel hub combo has a potentially different length spoke. Also, drive side length will vary typically from non drive side length