Regarding T206s, when it is complete is subjective to a degree. If you were to do a Kansas City subset, you could just collect one example of each front regardless of the backs. On your budget that would probably mean mostly Sweet Caparol and Piedmont backs. The tougher backs can get quite expensive even for low grade commons. To find out what backs are available with each front check here:
http://www.t206resource.com/Checklist.html
JimB