I want to earn money from Google Adsense. What factors I must follow that my site approval by google team.

My site about stories posting to UK & USA targeted country.
How many posts are existed before submitting to Adsense?
Do I Need SEO before Adsense submission?

It offers several services online. It offers a mail client, a document server, a search database, a book store, an app store, a calculator, a translator, a currency conversion, and several other services.

I am member of Google adsense account from the last 1 year, but my monthly earning only 40-50$ per day. So i want to boost my earning so please suggest any method, technique and any guidelines.