The most important lesson is that getting to space is easy. The hard part is staying there.
After 100 or so hours you'll manage to dock in orbit. This is about as good as it gets. MechJeb trivialises this (IOW means makes the game playable if you don't want to play space randezvous simulation) but I strongly recommend doing it by hand if only just once.
I agree up to as good as it gets. Building a in orbit assembled explorer to fly to Jupiter, land probes on all the moons, and fly in the Jovian atmosphere in a plane, then land your explorer on a moon to form a permanent base is about as good as it gets.
But yeah my suggestion is to play career mode where MechJeb is in a science node. That way you play and awful lot of the game without it. Docking without assistance is definitely tricky, which makes it all so amazing that people actually did this in real space ships and their real life on the line without any automation.
After 100 or so hours you'll manage to dock in orbit. This is about as good as it gets. MechJeb trivialises this (IOW means makes the game playable if you don't want to play space randezvous simulation) but I strongly recommend doing it by hand if only just once.