To answer this question depends greatly on where you are today, what SEO has been done before on your site, and what your competition and market levels are like.

As a general rule of thumb, most websites on page 2 can be brought to the first page within 3 months. As for a brand new website, with no domain authority, no online presence, you’re looking closer to 6+ months to get good first-page rankings on your market’s competitive keywords.

During that time your leads and traffic will increase gradually and regularly, but the big win is once you hit the top half of the first page.