I would think it really depends on how "rustic" you want to go, and where you plan on camping.
For example, if you plan on staying mostly in campgrounds with electric hookups, you might not need a large generator or any type of solar system - a small battery bank, or even just an inverter to plug in a laptop while on the road would suffice. Pull-in to camp, and plug in to power and water.
Depending on size and where you want to stay, you might or might not need a bathroom with a shower. (That could save space / money / plumbing.)
If you're planning on doing fair-weather camping, you might be able to get away without a built-in heating system - either use a portable gas heater, or electric space heater (if the campground has hookups).
It's also possible to do some things in phases if you decide you want some things - eventually - but not right now. (For example, if you wanted solar power, to be self-sufficient, you could plan on installing solar panels, and plan a place to put the battery bank - but you don't have to get the solar panels or battery bank now. You DO want to make sure you leave room to run the wires now. Appliances can be the same way - maybe down the road, you want a fancy stove of fridge, that might be expensive, while there's a cheaper option you could live with for now.