Do you mean buy ins of 50 big blinds or 50 big bets? Usually limit buy ins are expressed in big bets and 50 big blinds is equal to the standard limit buy in of 25 big bets, so I'll just assume the latter.
Even then it's not an exact science when using all non-denoms because you will want to nail down a structure (i.e., 2 chip/4 chip, 3 chip/6 chip, etc).
I prefer 3 chip/6 chip so assuming that structure, I will say you'll want a minimum of 1 rack of the lowest value per player. Let's be generous though and say that each first buy in is composed of only lowest denom chips. Then you'll give out the second buy in with the second denom, which we'll assume will be 20x the lowest denom. Then your third buy in per player (we play with degens, right? 3 buy ins each) can be with the second denom as well. If you're absolutely set on getting a third denom go for it but it's really not necessary imo.
So that leaves you with a breakdown for 10 players of:
1500 (x)
150 (20x)
However many you want (100x)
If you want to go a bit more conservative in your total set you can certainly get by with a rack per player of the workhorse denom and just do:
1000 (x)
175 (20x)
Whatever (100x)
If you want to get super, super conservative you can squeak by with 60 workhorse chips per player and do:
600 (x)
195 (20x)
A bunch (100x)
But part of the fun of limit madness is having tons and tons of chips in play imo. As far as what my group plays with, I wish I could change them, but they've been stuck for years in this structure before I was here. We play $5/10/15 (sometimes leaving off the $15 depending who hosts) with all redbirds. So a 1 chip/2 chip/ 3 chip structure. Yuck! But they're old and stuck in their ways and donkish enough to get an assload of chips in play anyway