how to get sponsored posts or contests??

It takes time.. build your domain authority, page rank, IB Rank etc.

write quality content with good seo. after 5-6 months time, when you are actually established with a custom domain , you can searcj for sponsored postsh

Ok..will try my best

You should concentrate on making useful content to your readers than be a platform for companies to promote. A site becomes big because of the readers who can relate and use your content. Not because of the brands.