It's getting harder and harder! But the answer is yes. You may certainly perform SEO on your own (DIY SEO) (Do It Yourself SEO). Anyone can learn how to conduct SEO for their business with some research and practice. Enter your URL into a tool like ahrefs to get started with SEO quickly, and then concentrate your efforts on the recommended action items. The more competitive the niche, the harder it will be to rank. A lot of niches these days have active SEO professionals operating within them, so be careful, don't bite off more than you can chew. The fast answer to determine whether or not you can make an impact on your own SEO is, how strong is the competition, and unfortunately for the untrained, determining strong competition is best done by someone with experience.