If you want to travel cheaply, I'd suggest starting with the Appalachian trail. I'm making that suggestion based on the way your question is written. You mentioned Colorado, a place well known for (among other things) spectacular views and radical contrasts in geographical relief. In other words, beautiful place, with most of its key attractions focused on the outdoors. You also mentioned S. East Asia. Most of SE Asia is extremely rural and undeveloped. You're obviously leaning towards some outdoor adventure, not restauranteering or shopping.
Sounds like you want to do some hiking, sightseeing, etc. For these purposes, I'd say the Appalachian trail is a great starting point for you. There's enough "wild" left in it to make it interesting, but still well-traveled and established enough, as far as trails go, for novice and intermediate hikers to be able to do large sections of it safely (one of your criteria).