The best value are the value rooms at AKV. You can book a whole week in a studio for only 69 points (during slower seasons). I'm renting one of these for my next trip and it'll be cheaper than the All-Stars or Pop Century! There aren't many of those value room and they go fast so owning there would almost be necessary but at least you could buy a smaller contract since you'd need less points there which would save you money. I've actually thought about buying points there but I, too, want to hop around so that home resort would only help me when I stay at AKV. And there have been reports of people being able to get them at the 7 month mark. Not always, but sometimes.
Boardwalk also has standard view rooms which are cheaper and go fast so owning there would help you get those. But again, there have been reports of people being able to get them at 7 months...though highly unlikely during F&W since they are so popular.
Owning at Saratoga gives you the booking advantage you'd need if should ever decide to bring friends or family and stay in a THV. Plus like others have mentioned, the dues are cheaper and the contracts are longer than others.
But if you truly wanted the cheapest points and didn't care about the end-date of the contract, then OKW (not the extended contract ones) are the cheapest on the resale market.
If you're not in a hurry and are good at negotiating, then all 4 of the ones I've listed can probably be had for a really good price. We've seen reports of some people getting SSR and OKW as low as $47 per point and BWV as low as $51 per point. The best you could probably do for AKV would be $69. But these prices are the exception not the rule.
If it were me, I would either rent points for your next trip or buy a small contract (like maybe 50 points) at one of the inexpensive resorts and use the bank and borrow method to use up all available points (150 points) to cover your next trip. That way you can visit the other resorts while you're there and see if you just want to buy more points where you already own or if you want to buy at a different resort because you fall in love with it and feel like you MUST own there.
And for what's it's worth....I personally think SSR is the best "deal". Good luck and let us know what you decide.