Hi Becky,
I love that you are planning your trip to the Walt Disney World Resort now for 2017! You really will be able to customize your vacation to your needs.
You can purchase
tickets now for 2017. Many guests do this so they can spread the cost of their vacation over a longer period of time or to save money in case ticket prices go up. Your ticket will not be active until the first time you enter a park and then you must use the remaining days over the next 14 days.
Two things to keep in mind. First, if you are buying a single day ticket, you need to look at park and season. There is a different pricing for single day at Magic Kingdom and the other three parks. In addition, there is different pricing on the time of year.
The second thing is the Disney Dining Plan. If you want the Disney Dining Plan, you will need to purchase a package from Disney. This will then allow them to link your dining with your tickets.
Wishing you a magical vacation!
Beth