Building web 2.0's on my own domain (subdomains) (worthwhile? or buy new domains)

So I'm creating a bunch of subdomains on top of my own domains. Is it possible to rank these just like it's a new domain (like a $0.99 cent .xyz) and do just as well?

Basically I'm building a mydomain.com which I'm branding as a blogging network for anyone who wants to sign up

But then I'm building my own blogs on subdomains instead of buying a bunch of new domains. Then I'm attempting to do different projects like spun content, duplicate content with canonical tags, even original articles mixed in.

Do I have a better chance of ranking if I just make $0.99 cent domains instead? Or should I be fine making very mixed bag of categories/content on different subdomains of my main domain?