If you are actually going to buy I would recommend getting as many points as you feel you can comfortably afford (meaning without raising other financial concerns). As most will say, they always wish they had more points. Also, you face the issue later of not being able to add on at VWL if you want more points there later because it will likely sell out in the next several months.
However, I sense an issue of whether you have a spouse who may not want to buy Disney. I don't do boats (give me terra firma to stand on whenever I go on vacation) so I cannot tell you whether other cruise lines are better than Disney but it is certainly the only cruise line that can give a Disney experience. Personally believe it is important that both spouses agree with the concept that they will be doing mostly Disney after buying. If there is unwillingness on the part of one, then you have a serious issue to resolve before buying.