This is my average Magic Kingdom day:
Assuming I can’t get Minetrain (and I usually can’t) I book my first 3 fastpasses for Jungle Cruise, Pirates and Big Thunder. In that order. Adventureland is near the front, so it’s an easy path right off mainstreet.
If my day is moving along nicely, I might squeeze in the Tiki Room while I'm still in Adventureland, if I'm dilly dallying a lot, I won't.
Immediately after Big Thunder, I pickup the soonest fastpass I can find for Haunted Mansion. It's usually still early, so I can usually get one within an hour MAYBE two. If the Haunted Mansion pass is right away, I ride it right away. If it's a ways off, I might kill time doing Country Bears. Maybe Great Moments in History w/ the Muppets. Sometimes Splash Mountain also, though I tend to go in the fall and winter a lot, so Splash waits usually aren't bad at all that time of year (people at times don't want to ride it in fall and winter, if it's sweater weather). In the dead of Summer, Splash would have a much longer wait, I expect, and I'd usually skip it. I'm not nuts for Splash, so I admit, I omit it a lot. But killing time usually isn’t an issue regardless, because usually I find a Haunted Mansion within an hour.
After Mansion, I grab a Small World Pass. You can usually find a Small World pass within 30 minutes of the current time. There’s no reason to ever ride Small World standby.
At this point, I’ve hit pretty much all my top priorities except Space Mountain and Minetrain, so I’ll do one of two things. If it’s a low crowd day, and Space Mt. has good availability (and is likely to maintain good availability, and still be available later) I’ll spend a slow afternoon picking up fastpasses for other things. Some character meet and greets (most of which are in fantasyland) or riding things like Pooh and Little Mermaid (also fairly fantasyland adjacent)… Eventually that slow afternoon bleeds over into Tomorrowland, and I’ll pickup things like Space, Tomorrowland Speedway & Buzz Lightyear, as it’s convenient. And I'll fill the gaps with Carousel of progress or people mover.
Now if it’s a HIGH crowd day, I’ll waste no time in picking up the soonest Space Mt. I can, and simply kill as much time as I need to ‘til it’s active. If the fastpass is a ways off, and I need to kill some time, again, I’ll do things like Monsters Inc, The People Mover or Carousel of Progress. If the fastpass is soon, no need to kill time. In either case, in this scenario, AFTER Space Mt. I start picking up rides like Buzz, Tomorrowland Speedway, or backpeddling into Fantasyland for rides like Pooh and Little Mermaid.
And at that point I’ve hit all my priorities, and it’s a good day. And it’s usually not even late afternoon yet. And I’ll just pickup whatever random fastpass I feel like from there on, for lower priority rides or things that aren’t a “MUST DO” for me, but I still find fun. (I’m a big fan of Tinker Bell, so I might pickup up a Tink meet & greet pass, and head on over to Maintstreet for Tink, A Parade, and a Chili Dog @ Casey’s) I might also go pickup a second late evening fastpass for Pirates or Haunted Mansion and ride them again, as they're two of my favorites. But by now... it's casual. No worries for me at this point in the day.
“What about Peter Pan and Minetrain!?” You may ask.
Well Peter isn’t a priority for me, truth told, as I’m an adult male, but I do ride it on occasion. Minetrain is a priority, but I usually can’t get a fastpass for it anyway, so it’s a moot point. In either case however, the answer is: You likely won’t see a fastpass for these rides available at a time that’s convenient, so you just have to hope you get lucky. If you see a pass, it’s probably worth derailing your best laid plans and grabbing it. Then course correcting from there later. With these two, you take what you can get and adjust as necessary. If all else fails, they both have better wait times late at night (after the fireworks), as lots of families with small children clear out of the park. Peter has pretty good fastpass availability late at night too TBH. I can’t tell you how many times I’ve gotten a Peter fastpass within an hour of the park closing. (Though the queue on Peter is awesome, so I honestly recommend doing Standby at least once if the wait time is 30 minutes or less)
ANYWAY… that’s my typical day at Magic Kingdom. Heck, that’s my typical Half-day at Magic Kingdom. Frankly if you get savvy enough with fastpass, you can hit all your priorities in half the time. In a full day, I just hit all my priorities, + about a dozen things I’d normally skip, haha.