Ink Options

I just purchased a Canon Pixma 7520 and will need to replace the set up inks it came with. I went on eBay and did a search for my particular model. Tons of 3rd party ink sets came up reasonably priced. However I don't know if this stuff is any good and or safe to use? I read on here about refills? How does that work and is that a safer option than what you would buy on eBay?

Thanks,
Naydeen