It varies, and we make no promises. Anyone who does promise you something is essentially a snake-oil salesperson. SEO requires patience, persistence, and time. Since these are simpler to rank for when we first start, we often target lesser competitive keywords with average quantities of traffic. We will begin to target the more competitive keywords as time goes on, and we will make progress on the less competitive keywords.
Ranking gains can typically be seen after three to six months, with lasting effects appearing after about a year. The beauty is that, if maintained, SEO rankings will be very advantageous for you in the future and will generate incredible ROI over time.