Studio in a warehouse. NEED HELP!

I have a warehouse space that I'm looking to convert into a studio. It has been my band's rehearsal space for the last couple years and now my band has broken up and I have the place to myself. I typically track pretty loud, usually between 90 and 100 db depending on what I'm tracking. Mixing is usually between 85 and 95 depending on the source and which step of the mix i'm on. I have very loud neighbors in this building (other rehearsal spaces). The building used to be an ice storage facility so all of the rooms are heavily insulated, but there is still a decent amount of bleed when a band is practicing next door. I would like to eventually build new walls inside of the space to help isolate the outside noise (and get rid of the cube-ness of the room). My main concern is that the floor is uneven concrete. There is about a 4" difference the low and high parts which makes it very difficult for a drummer to set up comfortably. When the ceiling gets higher, there is a step down on the concrete that is about 8" high. The floor is a concrete slab sitting on a floor made of 2x6's on end (2' concrete slab on a 6" thick floor). The walls and ceiling are made of some type of fiber board and 2x4 studding. There is a 5' section of brick on what would be the top of the diagram, and the rest is the fiberboard. I would like to make a separate control room and live room. It seems this would be easiest to do at the 8' mark as there are 6" posts about 10" off of the wall on each side. The walls were covered floor to ceiling with 3" studio foam (I got a ton of it for free), but I opted to remove enough so that about 30% of the room is covered in foam. I also built a few traps in varying sizes (again free) much like the 703 panels that I see on this forum but they are filled with pink fluffy insulation. They are in all of the corners of the room and above all listening positions where I have my monitors setup. I wont be able to afford a whole studio build at once, so i would like to do things in steps (tackle the floor, treatment, walls, etc. at separate times). I can at least work with what I have (and have been doing so for quite some time). As far as budget goes, I would like to spend less than $500 on building materials, and about $300 on treatment (for now). I realize that is not a lot for what i've got to do to make this space what it could be, but I would like to think of this as the first step of making it what I would eventually like, and when I start making a bit more money at it i'd like to finish more as I can afford it. As for an overall budget, i'd say less than $2,000 over the next year and a half.

"3" studio foam (I got a ton of it for free)," Free means it isn't acoustic, it doesn't provide isolate since no treatments do, and it is a waste. Welcome to the world of I told ya so.

The singer of my band worked at a foam factory and had a large order for a recording studio for which the bun of foam was custom ordered and what I have is what is left from the bun which they didn't use for that order. I am positive he did this without his company knowing but nobody ever said anything about it so it seems it isn't being missed. The large room has little to no flutter echo but the frequency response is far from even. There are many problems (lots in the low end, lots around 250, 800, and a spike around 2k or thereabouts.

the budget isn't going to do much - unless you can parley that into a lot of free materials and do all the work. on the isolation - if you only build a single wall to create the CR and LR separation, then scatter the absorption around the LR and in first reflection points and corners, you might get something a bit more useful. the bleed over - use close mic'ing. build some damped membrane platforms for the amps and drums to decouple and level them.

"I would like to eventually build new walls inside of the space to help isolate the outside noise (and get rid of the cube-ness of the room)." This is what you have to focus on. The treatments, are just that, treatments that are partial to specific / broad and other wise general frequency. Do not confuse that with the ability of a wall to >stop< sound. It isn't stopping sound the treatments are making the listener experience more enjoyable...but the sound is still moving in and out of your room, and in from other external environments. The isolation aspect is not best done as a "retro fit", it needs to be approached first...yea I know, it takes longer, costs more, etc. But the payoff in SILENCE...priceless :)