What is the basic luggage one should have if they plan on taking a maximum of a 2 week vacation, as in, how many bags? (Never traveled for longer than a weekend here, so I'm a bit confused)

Make a list of all the things you need for two weeks. Organise your clothes so they all mix and match - so you do not need to bring too many pairs of shoes or handbags(bulky).
Consider the location - will you need evening wear? Again, go for mix and match, so you do not need to carry as much!
Consider where you are travelling and how you will get there - will you need to carry your own luggage? If so, travel light.
Consider your washkit - buy small bottles of stuff, or get some small bottles and decant shampoos into them - that takes up less space.
Lay everything out on the bed, and then work out what size of case you need.
I rarely take more than one case with me - I have a small one, a medium one and a large one - the large one only gets used at christmas when I am carry presents home.
Next week, I am going away for two weeks and will take the smallest bag with me - because I will be staying with my parents, so can do laundry there, and do not need to carry as many toiletries.
Have a nice trip!

I carried one on and then had a personal bag (bookbag) with laptop, etc.

Was plenty for 10 days vaca

depends on the mode of transportation! Flights within the States only allow you to check one bag, carryon one bag and one personal item (purse/backpack/etc). International flights you can check two. Car: what the trunk can hold!

This depends entirely on the person.

I could fit two weeks worth of clothing (provided I would have access to a washer and dryer) and hygenic supplies, in a typical grocery store bag.

I've known people that would need four full suitcases for the same trip.

For a typical person, one good sized suitcase, and an additional smaller bag for hygenic/shower supplies is pretty reasonable. Two suitcases if you need just a bit more space.

The key is to compact, and pack efficiently. It is better to have two full suitcases with everything you need, than one suitcase, and 10 other seperate items (pillows, bags, purses...etc).

You want to be able to move it easily, so you are not bogged down with a huge logistical nightmare everytime you want to move your stuff from place to place. You're supposed to be relaxing remember?

That said, there is no set rule. Pack as much as you need to keep from worrying, but don't get carried away. The places you are going probably have washer/dryers, and supermarkets, and drug stores. After all, people do actually live there themselves.

...oh, and make friends with the "travel sizes section" at your local supermarket. You'll pay a bit more per oz/quantity, but you probably won't notice it...and the sizes are perfect for saving space and hassle. Plus, you won't feel guilty for using them up, and throwing them away so you have less to bring back.

I went to England on my own the first time for 2 weeks.

I had a carry on to put above my head on the plane, a purse and a medium sized suitcase :)

If you are not traveling by plane, i would say still bring that small backpack or duffle bag just in case, haha!

When traveling for an extended amount of time it is important to have enough space. I would recommend taking a 29in Rolling Luggage such as this: http://www.luggageone.com/store/p/26-Aspire-GRT-29in-Rolling-Luggage.html , I would also recomend taking a garment bag so that you have a safe space to store your outfits: http://www.luggageone.com/store/p/496-Baseline-Deluxe-Garment-Bag.html also a small carry on luggage is recommended for more space, one of the top models is the Xspace collection by samsonite: http://www.luggageone.com/store/p/41-xSpace-Carry-On-Spinner-Luggage.html .

I hope that helps, on that website http://luggageone.com you can find everything from all types of luggage to something as small as toiletry kits and hangers.