I am holding a small dinner party and have been checking on my glasses. I do have enough, but not a big variety. Does it really matter too much about using the correct glass for different wines, e.g. red and white, or whether or not flute glasses are used for sparkling wine (not champagne, I can't afford that)?

I am also considering serving port and brandy after dinner. Again does it really matter that I don't own any balloon shaped brandy glasses and what shape of glass is after dinner port served in?

I'm sure that your friends and/or family will understand if you use all the same kind of wine glasses for the various wines, etc...

You could look at a party outlet to see what might be available in inexpensive disposable "glasses", but those might be considered rather tacky by some.

If you have enough regular wine glasses, I'm sure that will be just fine

Wine glasses will be fine, even if you end up rushing out to wash them between courses. if that's going to be the case, keep a smooth surfaced towel handy for drying them, less lint to try to polish off of them.Please don't use the disposables, they affect the taste of the wine.
The port is traditionally served in either a large goblet or a snifter, which one seems to depend on location, but no one will be horrified at getting their port in a different glass. I try to avoid using jelly jars, but that's me
You don't say if your current glasses are the larger or smaller wine goblets?
When you do start collecting a wider array of stemware, buy flutes next,(sparkling wines lose their bubbles and their chill very quickly in those wide lipped flat ones, those are better for fancy-ing up puddings) then get the "other" winelass, then worry about snifters, sherry glasses,etc. If you buy closed stock, and care about matched stemware, get an extra pair for every 6 or 8 you think you'll need, and stash them away as replacement pieces.
One thing I used to get away with at my table was unmatched stems, I had a twenty or so glasses, in pairs or fours...if you're serving,let's say, 8 people including yourself, you can set each dinner pairing different glasses, I alway started at my own setting and paired my glass with the gentleman at my right,with the lady to HIS right beginning a different pair and so on... it would be easier to show than explain, but you get the idea? If you have 6 of one type at a table of 8 diners, you and the fellow at your right would get the odd lot.
Best of luck with your party!

Do you want bulk cheap glasses, dishes, cups, flatware and more kitchen gadgets, gew-gaws and all of that stuff. cheap, I mean dirt cheap compared to what you would spend in regular stores?

You won't find it at CostCo, nor At Pier One imports. Nope not even at Sears. You will find it at a 'restaurant supply store'.

Try a web search for that or Commercial Equiptment. You also get the best (in my humble opinion) cookware, heavy duty made to last and endure the constant use of a busy restaurant.

Then there are Caterers who will rent out dishes, glasses, and odd items for single use - some, not all.

Try looking under Party Rentals in the business directory of the telephone book. This last idea is just a single use affair and may meet your needs of the occasional party with lots of guests without havng to store a gazzilion glases, plates, etc.