This is what I use:
https://www.amazon.com/Owens-Corning-703-Fiberglass-Boards/dp/B005V3L834
With a little searching you should be able to get a case for about $100 shipped. You'll need 5 cases to cover 220 square feet.
The downside is that you'll need to cover it with cloth. I've used muslin with good results, anything similar that breathes will do, so see what's on sale at the fabric store. The easiest method I've found for wrapping these is to cut a piece of cloth long enough to fold over and cover both sides of the fiberglass, then sew up the remaining three sides with the fiberglass inside. To finish use upholstery pins to pull the extra cloth around back.
https://www.amazon.com/Dritz-9070-Upholstery-4-Inch-30-Pack/dp/B002LN9TS8
If you have space, you can get better low frequency absorption by placing these panels a few inches away from the wall or ceiling, so hanging them somehow would be ideal.
edit: You're welcome :P
Only online order was OC703, ordered from Amazon here: http://www.amazon.com/Owens-Corning-703-Fiberglass-Boards/dp/B005V3L834
I have a 9-5, so the acoustic panels took about 5 days of putzing around, cutting lumber, pre-drilling, measuring, etc. I'm sure you could knock it out over an uninterrupted weekend. The bass traps took about 2-3 days and was a bit more effort. I constructed 3 frames: one as a shelf to support half the roxul to the ceiling, one as a frame to attach to the wall, and one to cover in fabric which is held magnetically to the frame attached to the wall (really just for a cleaner appearance, and to hide the two frames behind it).
Wall panels were 24x48 (in reality like 25.5 x 48). The corner panels I'd have to go back and remeasure, but the distance across the face was something like 27" or larger (It's been a while and I don't have my napkin math handy). It's wider than the ATS bass trap because the dimensions of the Roxul Safe n Sound was wider as I cut corners out of the bats. I have 9' ceilings, and they are almost flush, save for a couple inches on the bottom where I have baseboard, and a couple inches at the top due to an angled ceiling at the edges.
This part is a bit tricky to explain as I'm not a whiz with the math. Using a reference sheet like this you can see which insulation type, thickness, distance from wall, etc., result in better absorption. ATS sells the OC703 I used for the wall plates, but I don't know what material they use for the bass traps. Looking at the above coefficients, you are best researching materials > 1.0 in absorption. However, this is a "all things equal" sheet, really only to compare materials to one another, and not really respective to positioning, room dimensions, and whatnot (see my TL;DR). That being said, ATS boasts 1.0 to 1 absorption on the bass trap, but doesn't list at what frequency range or how it was calculated. The Roxul Safe n Sound is indicated on the above link, but only at 3" as if you were using as a padding. Since you're stuffing it in a corner, you could take the depth as nearing 13". That's considerable absorption, but not consistent across the entire triangle.
A few weeks here and there before buying the OC703 and Roxul. Once I found enough supporting research that showed how you could build your own and be on par with most professional solutions, and videos that detailed the same methods and items, I bought the insulation. The rest was just "I have no idea what I'm doing" time fumbling through videos and documents. I'm not a genius when it comes to DIY but I know my way around the garage, so I think only moderate knowledge is required to build these without too much of a headache. I learned quite a bit along the way anyway.
TL;DR - something is better than nothing, and I wanted it on a budget with materials that were easy to acquire and frequently used online by others.