What is the best way of doing this?

I have 1 website already built for my niche, however, I am looking to expand a tad.

My idea was to purchase 10 niche related domains, and basically create 10 new websites, all niche related to try and increase traffic. Or my other idea was just to buy 10 domains and park them all on the original website.

What would provide better results do you think?

10 domains parked up will do nothing...

1 website is good, 10 is better if you have the resources (you will need 10x more content, 10x more links and 10x research)