Nintendo DS Lite actually. It was a Cobalt Blue and Black one I got in 2008. Prior to that I had never actually owned a console and relied on other means to do that gaming. Though Diamond was the first game where I not only got all badges but beat the E4. Prior to that I got stuck trying to get my seventh badge in Red. Got one or two gym badges in Gold, lol.
The earliest game I really completed was TCG for Gameboy really loved that. Soon after I got the DS Lite I also got a GBASP and brought all the games before selling them again. Now I wish to buy them all again.