I don't know if you can still buy a gold DS in stores, but I can help you with games. I just got a DS for Christmas and can't reccomend it enough.
For puzzle/brain training type games, obviously Brain Age is very good. Picross DS is awesome. It's extremely addictive, can be put down/picked up repeatedly, and has massive replay value. If you like crosswords, the New York Times Crossword game is pretty neat, although Nintendo is coming out with their own game soon. Puzzle Quest is also a must-have; bewjewled-esque with some RPG mixed in.
Since you like Zelda, get Phantom Hourglass. The controls take a while to get used to (only the stylus is used), but it's classic Zelda gameplay with some neat puzzles and even an online multiplayer component.
If you like rhythm games, Elit Beat Agents is offbeat but so much fun.
Other games that fit your interests: New Super Mario Bros, Sonic Rush, Advance Wars (Dual Strike or Days of Ruin, both are strategy games), Contra 4, and Castlevania: Dawn of Sorrow.
Enjoy :)
