It really depends on your specific needs and business goals. For example, if your website is not currently ranking well in the SERPs, and you are looking to improve that quickly, working with an SEO agency may be the most effective way to achieve that goal. However, if you are a small business owner with limited resources and not a lot of technical expertise, you may be able to do some basic SEO on your own. The key is to weigh your current resources and time availability to determine the best path for you.