step one- dig out a decent sized room and throw about 20 beds in itas a dormitory.
It will be a LONG time before you have more than 20 dwarves sleeping at once.
step two- this is the most important step. get your farm and liquor industry set up in OVERDRIVE. produce far more than you could ever use. if you're doing it right, your stonecrafter should churn out pots for about a year straight, trying to keep up.
step three- dig out enough 3x3 rooms for 200 some odd dwarves, i like to do it in two pods with 50 bedrooms above the dining hall and 50 below, with hatches that lead directly from the bedroom to the hall, one pod up high near the surface, and one down low where i want the fort to be later on. while you're doing this, cut down every tree you can find and buy every log you can from the traders to keep your carpenter busy making beds. You should finish the beds a bit earlier than you finish digging the space. then it's just a matter of hauling them and all the hatch covers and cabinets you've been making and BAM! you're good for a long time. (until economy is fixed, i dont think you need to make coffers.)
the beauty of this method is that your dwarves will be just fine sleeping in the dorm until you get shit worked out.
EDIT: too many migrants is never a bad thing. You'd be AMAZED how fast 40 masons can put up a whole freaking castle.