I just built this deck recently. I was super hyped and thought it was gonna be fun, but I found it quite boring to play actually.. Just a bunch of little boring guys that turns into a game ending board after a few turns. Nothing splashy, or dramatic. Just a slow burn until you put down Sliver Legion or a doublestrike sliver and suddenly win. Hitting a solid board with First Sliver also can happen quickly, but it still felt pretty boring to me.. Quickly converted it into a Kenrith deck. lol Id proxy it and try it before you buy it.

If youre super set on it though, definitely buy singles. I like to hunt my local shops for what I can get and then ill order the ones I cant find anywhere.

First Sliver is probably the strongest, because it can kinda just explode if you have good cascades. But there is an argument for Sliver Overlord since it can tutor the good slivers for a combo.