Don't get an r4 card. They were great, but newer games may need to be patched and still may not work. The r4 teams has stopped making updates.
About 6 of my friends have cyclo ds cards. It supports SDHC and comes with a 6gb card for $100! It's top notch.
As for games, Zelda is incredible, elite beat agents is worse than crack and mario kart is best when played in 8 player multiplayer!. The world ends with you got ds game of the year on ign and I truly haven't played anything so refreshing in a long time. You just have to play about 3 hours past the slow parts.
Space invaders extreme is impressive and addicting, ff tactics is incredibly long and fun, and picross is a fun puzzle game to play with a friend with only 1 card.
You buy a lite and a cyclo and you won't regret it or ever have a shortage of games.