I would try to get a used GTX 1060. The cheaper, the better. The more you spent on the card, the longer it will take until you reach the ROI.
As clock rate is irrelevant, the cheap models are fine as you do not need to overclock and hence do not need best colling solution.
Which RAM is used is just luck. Even on check cards from Palit and PNY you can have Samsung chips. Most 1060 seem to have Samsung chips.