I suggest you engage the services of a professional acoustician. The reason is, this is the sort of endeavor where knowledge and expertise will make far more of a difference than how much money you can throw at the problem. I have largely stopped giving out armchair-quarterbacking advice on room acoustic treatments after having heard the kind of results a professional can get.
Jeff Hedback of Hedback Designed Acoustics comes to mind. Jeff is an award-winning studio designer who is still affordable. He can tell you how to DIY your own solutions to save money; most of his studio clients are on a budget too.