Use the Fragrances Wanted board. Use trusted/top-rated sellers on ebay. Buy samples from Luckyscent and the Perfume Shoppe (latter offers five samples for CAD $15, which is good value despite the small range).
When you've worked out what you want to buy, go to http://scentsplits.wikidot.com/ and organise a decant. Don't buy decants from The Perfumed Court as they are rip-offs. Samples, sure, but not decants.