In part 1 in the series of room treatment I said that proper treatment is a lot more expensive than most of us can imagine. This is a no-joke as you’ll find out. For you who fell you might want to spend a little more, here are some links to get you started. These are neither the most expensive nor the cheapest options out there.
A very common material used.
Here there be bass traps…
A thing to attach to your micstand to kill of reflections.
A variation of the above.
I think it’s also important to mention that if you’re going to spend a lot of money on material, then you should bring an acoustic expert to your place. There is a lot of science behind this, and placing things wrong will not give you value for the money.