generating back links for a sub-domain with one page?

Few questions here, but I appreciate any answers.

I've created a free commerce website through ecrater so the domain is sitename.ecrater.com but I only have one page I can work on adding content/keywords. I did purchase a .com through godaddy to re-direct to the ecrater site.

Will this work when creating back-links using the domain I purchased to re-direct to the commerce site?

How effective will it be creating a twitter and updating it frequently for this site?

I think, you won't get any benefit of redirected domain. Since, this new domain does not have any rankings, backlinks and authority... SO, its better to create backlinks for your main domain only.

Check the community pages of ecrater as they address this topic in detail.
Many people have come to the same issue...

For my ecrater stores i just keep the same name and work seo on my regular ecrater domains...