Heyo, I also went to the law school and contended with this issue pretty much exactly (except that I work in public service, and don't get the big firm bucks).
My suggestion is not to buy a bunch of suits all in one go, as your taste in suits will evolve really quickly once you have to start wearing them every day, especially if you are around a lot of other lawyers in your firm, or if you are in court a lot.
For your first suit or 2, I would probably just buy two hickey freeman suits, which are fine middle of the road suits. They might be a little boxy, but they should be totally fine (I know a lot of people like the Brooks Brother's suits as decent starters, but unless they are on a deep discount, I have always thought they were not such a great bargain).
Just buy a navy blue, and a charcoal. Watch out for jackets that are too short! This is sort of a fad these days, but it is not where you want to start out with your proper suit ownership; particularly in a legal environment
Then, GO TO A TAILOR AND MAKE HIM TALK TO YOU ABOUT WHAT HE THINKS. In my experience, tailors are usually not very giving in conversations about clothes, but torture the guy and make him spell out how the suit looks and how it should look. I think this is a good way to sort of wrap your head around how clothes should look until you get your sea legs.
Then go to Brooks Brothers and buy 7 or 8 non iron shirts. Don't buy 8 copies of the same shirt, because you want to give the illusion that you have a broad range of clothes.
Then buy some Allen Edmond's Park Avenues, or something similar, and a belt that matches from the same shop (there is an AE store in NYC, so it might be best to just go in there, and skip the internet. The LA store has great customer service).
Finally, your taste in ties is also going to change fairly rapidly and they are fairly expensive new (I know you are making gumby bucks, but still, no need to flush it away). I suggest just buying a bunch of decent brooks brothers / faconnable ties off ebay.
I would probably buy about 10, which is a little thin once you start wearing them everyday. Once you have a better sense of what you like wearing, you can start buying them new, but in the meantime, you can get really decent / like new ties off the ebay for extremely reasonable prices.
Okdoke, I hope that helps, best of luck in the grind!