i was wondering which made a bigger difference to the strength of a BMX wheel, the rims or the spokes?
like what material they are, thickness, amount of spokes, etc.

help would be appreciated.

What makes the biggest difference is the build. If a wheel isn’t trued, tensioned, and stress-relieved properly it won’t matter how good the quality of the rim and spokes are. That said, the design and quality of the rim is probably the more important between the two options you’re asking about. You can’t really look at just those two, however, because the width and design of the hub is also very important, as are little things like the nipples. Overall, though, my answer is "rim" because its design and construction (including spoke count) is a biggie.

Hope this helps some. :o )