First, try to get a copy of Mr. Lipset's Encyclopedia of Baseball cards. Originally there were 3 volumes, #3 covered 20th century tobacco cards (that will have your T206 coverage). The reprint edition has all 3 volumes together.
Next, go here,
http://www.oldcardboard.com/t/t206/I...al-edition.pdf and download this pdf, put it on a jump drive, then go get it printed. Read it, then a week or so later read it again.
Buy 2 or 3 real white border tobacco cards, T206s, from someone who will be certain to sell you a real one. Ted Zanidakis could sell you a real one, he has more than his share of 'em. Quickly glancing at the list of dealers under vintage links you'd be save with DavidBVintage, Wayne Varner, Jay Wolt, Mike Wheat, Frank Ward, Kit Young's company, those folks would sell you a real card at a reasonable price. Once you have a few in hand it will be easier for you to ascertain authenticity, detect trimming, and stuff like that.
Patience and persistence are helpful attributes. If you buy 4 or 5 cards a month it will take you close to a decade to close in on the set. If you buy slow and set a few dollars aside, you can use the "setaside" to go after a lot on eBay or in an auction where several cards are offered in one lot.
Wish you well with it.