Honestly, it has a lot to do with luck. Using Ebay is really tricky and if you're buying it from a site such as Ebay, make sure you're buying from someone who is reliable, and by reliable, I mean someone who had 100s of trades with rating 95(if not higher)-100.
I got my games from the local ebay-like site, so I didnt have to pay for all the shipping expenses. Good side of this is the communication is easier, chances you will get what you want are higher, and th last and the most important ones, you'll get it for cheap. Downside is it took me forever to get the games. I was checking the websites regularly for a year or longer to get games such as Yellow and Crystal and even Emerald. Newer games are easier to find, but are more expensive.
I got all my games really cheaply, but it took me a really long time. They are wanted so they disappear in a day. In the past year, I've seen only one Pokemon White 2 which is next on my buying list, and it vanished from the site in like few hours lol. Still waiting for the cheaper one though.
tl;dr : Try buying it from a local store, or ask on website forums,social networks, ebay-like sites if someone is selling the games. Good luck!
