Another piece of excellent advice - know yourself. If you are a value driven person - you probably won't spent the zillion points to stay at BLT with a MK view over the holidays - so don't worry about it. Value driven people might fly in on Saturday, spend Saturday night at Pop, spend Sunday - Thursday at their
DVC resort (OKW or BWV Standard View rooms are bargains) - and maybe extend their vacation by going to Universal for the weekend with FotL privileges.
If you are a sharer, you might need twice the points of a non-sharer - or more. You know you are a sharer when your first thought is "we could bring my sister and her family." If treating your family and friends to rooms is a driving factor - you'll want more points - if you are looking at this idea and thinking "my friends and relatives can pay for their own vacations!" you need fewer.
If you are the type of person who thinks that four people sharing one bathroom is a human rights violation, you are going to need more points than someone who thinks that four people in a studio is perfectly comfortable (and if it weren't for occupancy restrictions, you could easily make six or seven work!).
If you live close and think that you'll drive down a few times a year, that's a different scenario than if you live in Alaska and know that every other year is going to be about what you can manage.
Think both short term - the trips you might take in the next two or three years - but build in long term flexibility (don't buy one huge contract) and think about the long term - that may mean you'll need fewer points long term (kids leaving home) or more points (want to use them for grandkids).
There are all sorts of DVCers - there are couples who stay in one bedrooms because they like the full kitchens, and families of four that fit in studios for two weeks at a time. There are people who want a Grand Villa at Christmas every year for a ton of points, and people who want a studio every other year for a week. There are people who MUST be close to the parks, and people who seldom enter them. There are people who use their points outside of Disney, and people who wouldn't dream of a vacation anywhere else.
Its easy to read about how someone else does it here and thing "wow! that sounds great!" But if it isn't you, you'll try it once and never do it again. DVC is something you need to buy looking at how you will use it, over and over and over again.