As a fellow n00b, I will offer a suggestion. Contact the nearest club, and see if they host a fall club sale. People tend to collect too many trees, and then don't want to deal with putting some of them back into winter storage.
That should give you very broad exposure to trees in all stages of development.
Snagging free stuff is fine, but it's going to be on the back burner for a couple years. Get some eye candy while you bide your time with some of these bushes and air layers.
Consider working backwards. The more developed a tree is, the more obvious the decisions will be regarding refinement.
A medium developed tree might have the major branches in place but you have to grow some more on your own.
A really nice ESTABLISHED stump will let you make all the decisions about branch growing or wiring right away
Something out of the ground...you're really just going to stare at it for 2 years.