You will go through the base malts (2-row, pils, pale, marris otter, etc) a lot faster than you think, so buy them by the sack, especially if you have your own grain mill. It also allows you to be impulsive. You can brew a lot of styles with Belgian Pale Ale (Castle) and pils malt (Briess).
I went overboard on the crystals--you don't need 5 pounds for each 10 degrees Lovibond. I'll let others chime in here about flavor differences between the various crystals. I doubt many can discriminate beyond low, medium, and high crystal ratings, and Special B/special roast.
The highly kilned and roasted grains are used so sparingly, that I don't recommend more than a pound. I still have a bunch of various dark grains sitting around after I bought them thinking I'd be doing a bunch of dunkels, porters, and stouts. Then, after recipe formulation, it became apparent that the dark grain contribution for each batch is often in the mere ounces (e.g., 1 or 2 on up to 4 or 8 ounces).
I do recommend aromatic and/or melanoiden malt--I use these in nearly all my batches, when appropriate. I love the maltiness.
I also second the large quantities of Magnum hops--they're a clean bittering hop with high AA levels.
Don't just get one or two ounces of a hop. Sometimes you need more than that just for one batch.
Fermcap-S (antifoam)--the best thing for preventing boilovers
I always forget to buy enough DME--they're great for yeast starters.