It depends if this is a new site or it is an established one. Whether you are expecting huge changes or slow yet constant progress. After fixing any technical SEO & onpage issues in the beginning and implementing SEO strategies you can start observing some improvement in 3 months' time. Google Core updates happen regularly which causes fluctuations and there are many other factors which in my experience put a time span of 8-9 months for getting good results. Although, this will only happen if you let me stay focused on a particular goal, and let me implement my strategy without much interference. I encourage meetings for discussing the reasons and impact of what I am doing.