For a PVC booth, which I'm assuming you're making -- the number for effective sound treatment is 10 pounds per side. ie. Left, right, front, behind, top. 10 pounds per layer. About 50 pounds total.
Front X Left X Right X Top X Back
That comes to 1 vocalbooth blanket per side (it weighs 10 pound per blanket)
ie 1 on the top, 1 on the left, 1 on the right, 1 on the back, 1 on the front
(5 blankets total)
or
2 Suremax Ultrathick blanket per side (5 lbs per blanket)
ie 2 on the top, 2 on the left, 2 on the right, 2 on the back, 2 on the front
(10 blankets total)
or
3 Standard 2 3/4 pound blankets per side (ie 72X80, 2.75 pounds each)
ie 3 on the top, 3 on the left, 3 on the right, 3 on the back, 3 on the front
(15 blankets total)
I've tested Suremax blankets and Vocalboothtogo blankets and it's a matter of preference. If you layer the moving blankets, it'll perform just as well as Vocalboothtogo blankets.
Here's what's great and not-so-great about Vocalboothtogo blanket.
Pros: It has grommets. Very handy to have. (Assuming you buy the grommet version). It's cleaner and less hassle. It's easier and quicker to hand up 1 blanket per side. Rather than dealing with 2-3 per side. It works.
Cons: They don't pay for shipping. And when you factor in the cost of shipping, it's not worth it imo. It doesn't perform better than moving blankets if you stack the moving blankets. 3 moving blankets will perform just as well as 1 Vocalboothtogo blanket.
TLDR:
Budget: Get Suremax Ultra thick. Get free shipping yay. Buy the 10 pack.
Baller: Or just go Vocalboothtogo. Be sure to get the grommet version. Much easier to hang.
If you get the grommet version, it's much easier to move the blankets like a curtain if you use carabiners and rings. Much easier to deal with than clamps.
Carabiners
https://www.amazon.com/gp/product/B0819NX8G4/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
Rings:
https://www.youtube.com/watch?v=d4GQcR6LHSM
Old vid showing carabiner + rings