Welcome to the site, and welcome to the addiction as well
I'm only 40 cards deep into my t206 set and the guys who posted before me are all right .... patience is key here. And any certain card you are looking for is prone to pop up anywhere. It could be on ebay, could be in the net54 b/s/t section ..... it might just come at you in a pm or a card show. Wherever it comes from, buy what you want at the price you want.
As long as it meets your money and condition criteria, there is no "bad" place to acquire a card for your set.