For dries I like a fine synthetic dubbing like Super Fine- it's available in two different 12 color assortments in dubbing box for around $16 or individual color packets. The synthetics don't wick up water and just a wisp of it will make a nice slim body.
For nymphs and wets i like something a bit coarser-- mostly i just use a natural Hare's Mask, but Haretron or Haretron Plus (with some synthetic flashy material added) is popular.
For someone just starting out and tying traditional patterns, I'd get a natural Hare's mask for nymphs and then a 12 color Superfine Assortment for dries (since there are 2 different Superfine assortments I'd get the one with black, brown, blue dun, blue wing olive, amber, light cahill, mahogany, brown olive, adams gray, olive, pale evening dun, and hendrickson pink to start)
A natural color mask will have several shades of earth tones/colors you can pick from.