Define successful. Do you mean riding as many rides as you can? My idea of successful is most likely very different than others. We never buy
Genie+, we also never try to ride as many rides as we can. On any given trip a successful day for me might actually be different then it was on another day.
But, a good day for me might be:
I never rope drop unless I just so happen to be up and ready just because I woke up early and thought why not. Even if I'm up early, I'm not a fan of crowds so I tend to wait a bit. Let's say I'm up, had my coffee, gotten dressed and I'm at a WDW resort so have early entry. I might get there at the end of early entry and find a place to grab something to eat and sit and eat and just watch the crowds. I do basically the same if I've slept in, I never get there at rope drop, I don't need the running of the bulls. I might look at wait times on
MDE and walk over to a ride that has a lowish wait, maybe 30 min. Rinse and repeat. I'm a big fan of breaks at the resort and park hoppers. Now that we will be able to hop any time, if a park is too crowded I'll just hop out and go somewhere else. I usually go back to my resort a little after lunch or around lunch, eat at the resort or another resort, go to the pool for some quality hot tub time or to the room for some quality rest time. Then around 3 or so, head off to some other park. Rinse and repeat. If I have longer than a 4 day trip, I can ride every ride I want to just by park hopping. I also love to watch shows so I scatter them in throughout my day and scatter in some time to just enjoy the parks. I like to go slow and take in all the details. I never make ADRs in advance, maybe a day in advance if there is somewhere I really want to eat, otherwise it's just day of while walking around. Park Hoppers come in handy there because I can eat in any park I find an ADR I want for. I can also eat at any time I want since I don't usually have kids with me. I have never not been able to find a same day ADR somewhere and I like finding new places to eat. For me, it's all about not having to be anywhere at any specific time, thus no Genie+ or advance ADRs, it's all seat of the pants go with the flow. I also rarely stay until park close, again, don't need those crowds. I will watch a fireworks show every once in a while but if I'm at MK, I'll find some out of the way place to watch it instead of right in front of the castle in the crowd. Unless you are behind a pole at HS, you can see that show from anywhere in the theater. Epcot is mostly in the sky, with a little bit of water projections so again, anywhere. Since I'm not usually right in the middle of things, I can just sit and wait until most people are out of the way to make my way out of the park.
If you are about the rides, just pick two or three must dos and anything other than that is extra. Also, find out what they think they want to do and don't over plan or just plan things that you think they might want to do.