A simple 3-month SEO strategy is usually broken into three phases.
Month 1: Focus on the foundation. Do a technical audit, fix crawl errors, improve page speed, optimize titles/meta tags, and perform keyword research so you know what topics to target.
Month 2: Start publishing and optimizing content. Create blog posts or landing pages based on your keyword research, improve internal linking, and update older content that can rank better.
Month 3: Build authority. Work on backlinks through guest posts, outreach, directories, and promote your content to gain visibility and traffic.
In short, the first 3 months are mainly about building the foundation, creating optimized content, and starting link building. SEO results usually start showing gradually after that.