Find a large bowled, tulip shaped glass that holds at least 12 oz (but preferably more). You can use this for both white and red. This shape will give you enough room in the glass above the wine (only put 4-6 oz of wine into the glass at a time) to allow the esters and other chemicals to develop and concentrate before entering your nose allowing you to really taste and smell what the wine is showing. Crystal gives clearer sensations than glass, but is much more fragile. I personally use glass (Reidel Restaurant Series Riesling/Sangiovese glasses to be exact) because of durability and dishwasher safety, but the crystal versions do make a difference in taste (a difference I am not willing to pay for in either initial cost, or for the inevitable replacements).
There are many shapes available, and some manufacturers claim (with some justification) that different shapes are required for different grapes. This is true to a point, but in the end, do you want to spend your money on a cabinet full of stemware, or a cabinet full of wine?
In any case, the bowl should be as large as you can find, the glass should be as thin as possible (glass will be noticeably thicker than crystal) and have as little "lip" (the bead of glass or crystal along its rim) as you can find.
Always buy at least six glasses at a time! You will break some, and sooner than you think. A bottle of wine divides fairly neatly into 4 glasses when you use good large stemware, allowing you to serve a glass each per bottle when having another couple over for dinner. If you break one out of a set of four however, you are left short. Buy in sets of six, and you will have spares around. They mostly break during washup. I make it a policy not to wash my expensive glasses the night I use them, since inebriation leads to broken glasses! Leave them for the sober light of morning and your risk of breakage goes down drastically.
I recommend Riedel and Spiegelau, although there are many quality manufacturers. Expect to spend $8-12 per stem for glass and $10-50 per stem for high quality crystal. Please avoid cut crystal, however. You want a smooth surface that allows you to see into the wine to appreciate its color and viscosity. The glasses that your grandmother bought for your wedding present that match your china are NOT good glassware for wine appreciation. Pour the kids sparkling grape juice into them at Thanksgiving, and break them out when she is in town, but do not put good wine into them unless you are socially obligated to.
Good luck!