I' m not sure I exactly understand what you're asking, but I'll take a stab at it.
There is no
DVC at the Poly. If you are willing to stay at another deluxe resort - such as BCV, BWV, VWL, or AKL - you could book two studios for your time assuming they were available at the time you show up in the Member Services computer.
If you are determined to stay at the Poly on points, you can pay a $95 fee and use points there, but you would need a lot of points.
If you buy direct from Disney, you will be in the computer very quickly and will be able to make reservations almost immediately. If you buy resale, the process will take a few months - probably three - before you are in the computer and can make reservations.
One of DVC's biggest strengths is the flexibility of the points. You can reserve two studios for the same period of time, you can reserve a grand villa and a one bedroom at the same time... you can reserve as many rooms as you currently have points to do. You can use up to three years points at once if you bank from one year and borrow from the next.
If you are going every two to three years, start with a third as many points as you think you will need... then add on if it turns out not to be enough. Of course, the problem with that is that Disney has a minimum number of points you need to buy if you are buying from them directly. I believe it was 160 for a while, but I've heard of people buying 100 point initial AKV contracts.
Whether you buy resale or direct, there is no difference in how Disney treats you once you are in their computer. It matters for initial financing, incentives, and how quickly you are in the computer.
I'm not sure what discount incentives you are hoping for with a 50 point contract resale. It isn't likely to help you at all with your Poly trip. 50 points might pay for one night at the Poly. You don't get any incentives if you buy resale.
Hope some of this helps.