Prism of belief is the worst gamble in the entire game.

In 3 leagues, over 600 prism of beliefs. I have had one Prism that's actually worth anything. This is by far the worst and most bait gamble in the entire game thus far and from my perspective needs to be changed. It's a 1 in 3 to even hit that +3 and then the amount of skills 0.o at least when you get a sublime vision or watcher's eye in PoE 1 in the odds are MUCH MUCH MUCH better. This gem is literally so varied that it's next to pointless to ID them. Even with some of them being worth multiple mirrors it's a complete waste of time, you could literally sell unid ones a dozen times over and buy multiple versions of the one you want before you actually hit one.

So items like this is why I'm convinced this game is balanced around trade.

Basically the top end of this game is meant only for players who put a lot of time in to buy expensive items, or trade a lot (which usually require lot of time) to earn enough currency to buy expensive items.

Personally I would just ignore items like prism of beliefs. Play the game until it stops being fun, and only do things that are fun.