If you really want to skimp you can get go to your lbs and get:
- cheap top mount shifters
- front and rear deraileurs from the used bin
- used brake calipers
- brake & deraileur cables and housing
- used crank set (I'd go with a triple and check out a fitting site for the right length, when I went up to 175 I felt a HUGE difference (I'm 6-1") from the 170s - I'd never go back) and:
- have them install a sealed bottom bracket so you can have them worry about the right spacing based on the cranks
- ($10 shifters, $40 deraileurs, $25 for brakes, $25 brakes and housing, $25 for bb, $25 labor, $25 crank set, $20 for gently used chainrings laying around (or could spend $60 for new ones there, get steel they're much stronger (I've bent the aluminum ones))).

brake handles ($15)

cassette ($20) and chain ($10 - 6/7/8 are all the same size and are thicker than 9 and 10 speed (which I tend to snap).

Total on the 'group' - $215.

Another option is to buy a 'group' which will be all those things together and better shifters that will probably start around $400.