Right now, after you purchase a resale contract, you would be able to purchase just a 25 point add-on to become a direct buyer. You can get OKW or SSR for $140/point, so $3,500 for the ability to then get all the benefits and discounts. While Vero Beach and Hilton Head are priced at only $110/point, their maintenance dues are much higher, so might end up costing more in the long run.
Animal Kingdom seems to have some of the best resale pricing right now, and direct is $160/point. If you buy resale there and then want to add-on, it would cost you $4,000. A bit more than SSR or OKW, but not really a lot in the grand scheme of things.
I would highly recommend buying the same resort with the same use year that you bought resale, even if you have to go on a waiting list to buy. That way, you get all of the points at the same time to use at the 11 or 7 month windows. Don't let a guide tell you that you can only buy Poly or Aulani. You can buy points from any resort (well, except VGF since they have now closed the waiting list).