How much time it would take to be on first page?

I have a client asking me to set his 500 keywords( nearly 0-10 volume According to Moz) on the first page. I did on-page optimization and watch the balls rolling some of the Keywords came to first n second page.

What more i can do?

For every keyword to be on first. I ask for 3 months time and $500 is it fair?