Depending on how many days you're there and whether you have hoppers or not that could change the recommendations. The thread linked to gives you a good idea of how important FP are for each ride.
Here are some thoughts:
MK: You'll probably want to use at least 2 days of your FP for this park (assuming you'll be in the park each day you noted above). You'll definitely want Splash, Space, Big Thunder, 7DMT. I recommend any day you start at MK, to make your first FP from 10-11 or there about. If you hit rope drop you'll have a really good first 90 minutes with very few lines. I like making Splash and Big Thunder consecutive (i.e. Splash at 10-11 and BT from 11-12. Try to hit Splash at about 10:45 after you've done a few standbys during the first 90 minutes and then it'll be time for BT when you're off. Make the next FP at 12-1 and you can do a couple of low line rides between BT and that one. Once your 3 are done, you'll be able to get a number of other FP for 2nd tier rides fairly easily. PoTC, Jungle, Haunted and Peter Pan can often have long lines so I recommend using your add'l FP for those. But we also often did things like Small World or Under the Sea - even though those lines were only 20 minutes, we could get a FP that was effective immediately so we would take it and then make another. If you were like us for our last pre-baby trip, we wanted to do the thrill ones more than once. We either used a FP on another day or we would on a non-EMH evening head back to MK for the last few hours (especially when it's open until at least 11 on a day with the last parade at 9 - you can walk on to a lot of things that last hour - we rode splash 4 times).
Epcot - Soarin will have likely just opened. I still recommend just getting to the park at rope drop and heading right there instead of using FP. There aren't enough FP options to make it worthwhile. However, if you love Soarin you may want to get a FP for it and still do it at rope drop to get to do it twice. Of course, if you don't have hoppers then just get Soarin, Space and Earth. The last two probably won't have much of a wait anyway. If you do get a Soarin one - do TT at rope drop. Also with Epcot, it's a great park to head to in the evening after you've used FP at another park. We spend a lot of time in World Showcase which has no lines to speak of (unless the Frozen ride is open by then). Lots of entertainment options as well.
HS - get RnR or TSMM and then Star Tours and Tower. Although RnR has a single rider line - more fun to do together.
AK - Definitely Safari and Everest. If you want to do Kali, I'd get that as your 3rd. Dinosaur isn't that long a wait often.
If you're there 6 days (not sure if you're in park all those days) I'd do FP 2 times at MK, 1 time at AK, 1 time at HS. 5th day Epcot (doing soarin and TT at opening and then Soarin a 2nd time with FP). 6th day do whatever you think you want to do again.
