I do it all the time.
I'd suggest laying in a "bench stock" of balsa. Driving to the LHS all the time costs money, too.
My source is Balsa USA, in the UP. They grow good wood up there. An e-order generally hits my porch within two postal days. Wood from Texas and Iowa flys, too.
I analyzed all the sizes and decided that 48" x 4" is the best buy, considering scrap losses from cutting smaller sheets. Just estimate how many sheets you want for starters, from 1/16" up through 1/2".
Add in some square stock, 1/8", 1/4", 3/8", and 1/2". A sheet each of plywood, 1/64" through 1/8".
You'll spend less than the price of one kit and probably be able to build four or five planes.
Replenish as the stock dwindles.