I'd agree with the bulk of the consensus here. I'd buy resale first then buy 25 retail second. You cannot use non qualified points even if some are qualified, unlike Bluegreen for example. I don't believe in the "buy where you want to stay" mantra because many don't actually know where that is when buying and almost 100% of those new to DVC don't know but often think they do though some will GUESS right. I'd suggest buy where you don't mind staying though for those who are knowledgeable and have experience, they can be the same thing. Never buy for cash type exchanges, there has never been a time in DVC history where it made sense to do so and it's infinitely worse today than it was early on. The actual value of what you're give up is still what it is today, not what one paid 10 or 20 years ago though for those who own with the options, it can make sense in a very limited number of situations.
IMO the best way to do this is about 6 months of active investigation, have a certain amount of on property Disney experience and at least some DVC experience. Usually this means at least 1 or 2 DVC rentals of some type either in the past or going forward. One of the big mistakes many new to DVC make is trying to get that next trip on points and count that as part of their savings. Usually that means they make poor choices of home resort, contract qualify, retail vs resale and number of points. If one is going to buy without going through this process, I'd buy the best value and best UY regardless where they think they want going forward, normally that's SSR. Then give it a try a trip or 2 then see how it goes. For that plan, I'd delay the retail purchase until the longer term plans are settled. But I do agree that the best situation, when one is knowledgeable enough, is to plan the resale and retail as a package and buy the resale first. Don't forget UY can be VERY important and where it's not, everyone is taking more risk owning DVC than if they could chose a good UY.