Disclaimer: I am NOT an expert...LOL
I would plan on one day for each park, with one day left over to go back to your favorite. In our case we are planning 5 park days: 2 MK, and one each Epcot, MGM, AK.
What are the days of the week? (Mon-Fri?)
touringplans.com has a "best days" calculator on their site to figure out which days of the week are least crowded for each park according to what time of year you will be going. I took that into consideration when planning. For example, Thursday is EE day a MK, so you would not want to go to the MK on Thursday. Tuesday, Wednesday, and Friday however, are less crowded. You get the idea, right? That may narrow down the choices of which parks in which order for you. Even if I wanted to go to, say, AK first, but my first day was AK's EE, then I would choose something else, for example.