Hello and welcome to the RTA forums !

A road trip is a personal experience and there is no one "best" route or stop as we are all different. What we can do is make suggestions to help get the best from your chosen route or places of interest, but with so little info it would be taking a shot in the dark.
How long have you got for the trip, is it one way or a return journey, what are your interests ? I would have a search of the forums, look at the map and get some general ideas and give us some more info to go on and we can certainly help you piece it all together for a memorable trip !

There is certainly no shortage of some amazing National parks.