This depends on how often you plan to visit Disney World, what size accommodation you would need, and what times of the year you want to visit. The Disney Information Station maintains a DVC Point Calculator and a DVC Point Chart. I suggest that you enter in some sample information, based on what type of vacation habits you have, to find out how many points would be appropriate for you.
Many ask if Disney Vacation Club will change the point requirement for a stay at a DVC resort. While the total number of points sold at the resort is a fixed number and cannot be changed, point needs for stays can be changed. However, if points needed for some nights (or room types) are raised, other nights (or room types) must be lowered, as the total points required to stay at the resort for the year cannot be changed. This has occurred only once, in 1996 at OKW, and is likely to happen only if necessary to keep resort utilization in balance for the benefit of DVC members. At that time some nights were raised a few points, some were lowered a few points and most were not changed at all.