best amount of pts? depends on how many you would use for a typical annual (or every-other-year) disney vacation. people differ on expectations. if you want enough for a studio at OKW for 5 nights a year, you could get by with fewer pts than if you prefer to spread out for 2 weeks in a 2BR concierge at AKV.
the minimum direct "add-on" (an additional purchase
if you are already a DVC member) is 25 pts...
BUT you may add 29, 32, 47 or however many pts you like. if you add fewer than 50, DVC will not finance and you must pay cash.
OTOH, to buy into DVC directly as a nonmember, the minimum is usually 160 pts, although AKV is running a 100 pt special right now. (you may buy a resale contract for any resort and any number of pts you want and can find available.)