Figure out how many theme park days you want. Is one day per park enough, or do you want a 5th day so you can go back to MK (or wherever)? Will you want to take a day off (we usually do), and if so, will it really be non-park or will you go to HS for Fantasmic after kicking back by the pool and relaxing all day (or skip the park totally and maybe play mini golf and then have the evening at Downtown Disney)? If you are looking for a down day, is going to a water park your idea of fun and will it be a relaxing time, or will it be as stressful as going to a theme park? Are you crazy about virtual gaming and dying to go to Disney Quest? Only you can answer these questions, but remember that if you are only interested in the water park, it's cheaper to buy a day ticket for the water park than to add on the waterpark and fun option.
Park hopping will depend on how you want to use your FP+ options. Now that there is the option for 4 and more, I would skip hopping and stay in one park. That's our plan for October (at this point). I'm going to save that $60 per person and use it to buy good things to eat at the Food and Wine Fest!
For our October trip, we arrive around noon on a Saturday and leave the resort by 10am on Thursday. I have purchased 5 day tickets, so we can go into a theme park on Saturday evening for awhile. We will go to one park per day, Sunday-Wednesday, and hope we don't wear ourselves out by not having a "down" day. I am hoping to squeeze in a visit to JellyRolls if they are open, as we are going to Disney to celebrate my DD's 21st birthday. As I said above, we are not going to hop or do a water park, as we aren't there long enough.
Try to think about what you want to do, and how long you will hold up in the Florida sun. Most people walk 6-10 miles in a theme park, but don't forget that you'll also spend time standing in one place in line, which is also tiring. These are things I think people forget to consider when buying park tickets. And remember- you can always add a day or hopping or water park admission, but you can't un-do them from your tickets once they are purchased!