Bitcoin is for slow growth and heavy investments. Litecoin, maybe - who know?
DOGE coin is going very viral and its just been 9 days, so there is still oppurtunity.
I mine DOGE coin, but I can't imagine it having much of a future after the hype dies out.
The media exposure of Dogecoin seems to be huge. For me it was the thing that made me actually download a coin wallet client and a mining program and see how they work. Maybe I'll even buy ~10$ worth of dogecoin and hope for their value to go up. If it won't, having thousands of dogecoins has some novelty value.