How much have you spent on drum gear? it's worth spending some money on good In Ears Monitors, especially if you are gigging.
For $50, I don't really think you're going to get something very good. The universal with the best isolation seems to be the Etyomic ER-4, but as a drummer, you probably won't be impressed with the low end response. And they are above your budget anyway.
I've found that (as a pro musician, both guitarist, singer and drummer) that no universal I've used has stayed in place.
A pair of IEM's might provide good isolation at first, but after you've been rocking out, pounding the drums and sweating under stage lights, will they still be in place? or will they start sliding out? Personally, I'm sick to death of ramming my UE super.fi.5 back into my ears during gigs.
So I've ordered a pair of customs. I've spent lots of money on gear, and I think that $500 on a pair of IEM's that aren't going to come loose during a gig is a goo investment. I got a pair of 1964-T with soft canals. Only a week or two to go.