Start with your plan. Where each component lives and why. Variables are leakage, wiring, access and traffic plan. Place exotic synths, like laundry, power saws and HVAC, carefully. Treat them like instruments. Like with drums, you need to worry more about sound getting out than in more than vocals, where leakage out is less a problem than leakage in. You probably don't care if the furnace room hears drums, but you don't want squirrel cage rumble on the flute track. Longways down the center of most houses are the aortas, Plenum for heat, home runs for AC, plumbing and data. AC itself is "noisy" one way, low end, but the wires can carry interference too. Data can be noisy in the mid and high ranges. Pipes creak, as does ductwork.
How many spaces? If you can dual use a space, it's not as good as getting three boxes checked with the same square, no, cubic footage. A mic in a well planned bedroom might be much better than a mic in a closet sized dedicated booth. Think in 3D, especially in terms of sequencing. Wiring tween the hard ceiling and floating ones has to be in place before you rock the inside, maybe fore you stand it up. You will need to add cables to your main runs, trackroom to control room, control room to data room, etc. Wasting a swath of space end to end on a walkway might not work as well as a short, walkway tween two rooms you want especially ignorant of each other, and dead end up against oh , maybe the tracking and listening rooms. Done right this hallway can land under the existing main cable runs and give you future access to your wiring too.
As you design your blueprints, you're going to see every future stack of materials flow in there, in sequence and know how its coming in, where it gets modified, how it becomes building, and where the scraps go after. Price your isolation wall lumber in 2x4, 2x6 and 2x8. Double the 2x4 quantity and compare prices. The sixes and eights can be ripped to make dual wall frames if you have a worm drive saw, some duct tape on your guiding index finger, and a steady sense of pressure. Different thicknesses, here and w sheetrock too. Fast light staple gun for faced insulation. Big price break if you can use precut studs, over lineals. Remember, you isolation walls don't touch the hard ceiling. In a non isolation wall, plan on cutting each stud to heighth over varying concrete, pin plates to slab and joists, measure and toenail studs into place, 16 penny nailgun a must. Strap bracing on the walls keeps the freestanding quiet rooms plumb. Two diagonal straps in opposition only have to resist tension, so you don't have to notch studs, and the straps themselves are cheaper than 3D section braces.
In the beginning, you'll be making dust and noise everywhere, but over time, you need a dust containing tool room to fall back to, as mods and upgrades will be going on long after studio operations begin. That can evolve to a soldering desk, testbench, and even a control room or audio routing nexus for the whole house. You may not want this on paper but wires go just as easily floor to floor as they do room to room. Any good general identifies key terrain and undertakes operation to secure territory, while civilian's inertia is tempered by long term memory issues, encroachement is a viable mid game strategy.
Think also about how you use the studio. Is it a private escape, or the focal point for the whole house and lifestyle? Are listeners sitting or dancing? Is your mixing desk and roaming cables up to dancer's heels or have you planned for public and not public areas? Basic needs, restrooms can be an issue in a basement, we haven't trained water to flush up at this point in evolution. Place to sit a fridge, microwave, and a non-audio circuit to plug into? Microwaves have brains and are designed to beam RF, and mine BEAMS brain noise too.
Almost done planning now, only one more decision.
What are you?
Musician?
Studio builder?
Studio operator?
Industry magnate?
On what day, and at what time, will construction operations cease and the above lifestyle commence?