easy! on that budget (if you can find one) a Universal Audio Solo 110. the lo-z button just slays on dynamic mics, and it has gain out the ass, and colored from clean to mushy depending where you dial the knobs. the smooth (warm) clarity of this preamp seems to be tailor made for vocal recording. it's a shame these are discontinued. yes, I have used this pre with an SM7 successfully more times than I can count
might be hard to source one, though. I would bet the Daking Mic Pre One is a very good, more readily available option. also on the forward/smooth/ballsy type of sonic territory. a nice single channel, transformered solid state preamp would seem to be hard to go wrong with, as a do-all "money" pre / piece of equipment on a budget. you can do a lot with one channel especially if you are layering tracks one at a time
pick up a Sytek, too, and get a mic collection brewing, and you should be able to learn a lot and record a lot, until the eventual day when you can start to add APIs etc, if you get that far. the solo 610 is also an excellent one to have around (not for vocals, though, if you ask me)
if you are buying this thing for vocals mainly, you should look into a channel strip rather than just a preamp. i use my sm7b with the ssl alpha channel sometimes as a vocal chain. its nice because it has the vhd feature which lets you dial in harmonic distortion.. nice for coloring vocals. plus it has 75db of gain which is plenty.. i actually also own a 003 and some presonus gear and they definitely wont cut it for the sm7b. i think presonus only goes up to around 58-62db or so. the eq is pretty nice too, plus the light limiter makes a good safety net when used very very very minimally if your vocalist gets loud real quick. i know its above your budget slightly but it would be worth it in my opinion.
by the way grace pre's are good transparent pres, but for this setup you would probably prefer a bit of color, or at least the option to add it if you see fit for the song