There is no longer any realistic way of doing search engine optimization "by hand" and without any tools; the closest we have to such a panacea would be an old school public relations wizard who is so deeply connected that he can go out to lunch and return with inbound links from The New York Times. All SEO professionals rely on a set of tools, often called a stack, to let them complete projects and pay the bills. Some people will swear by stacks that are 100% free; others insist on paying at least one subscription while another segment believe that one paid software suite is all they need.
Let's take a look at some of the free tools available now; the following stack will not cost a single dollar, and it is highly functional to a certain extent:
In the toolbox above, you can upgrade Ahrefs, Wordstream, and even Google Analytics with paid monthly subscriptions, but you could also make the best effort to thoroughly learn how these tools work for the purpose of getting the most out of this free stack. Keep in mind, however, that there will always be competitors who also set out to learn their toolbox inside out, and once they start paying a monthly subscription, they will have access to more functionality, thus making it easier to leave you behind.
Some SEO professionals feel that spending somewhere between $80 and $100 on Ahrefs is the sweet spot; everything else can be free, even SEMRush and Moz, but having too many competitors with paid subscriptions to Ahrefs will at some point affect your business model. While you can do onsite SEO checking with the Google Search Console, you will want to back it up with an opinion from Ahrefs.
Another tool that is worth paying for is a Googlebot simulator such as Screaming Frog, which is a very reasonable monthly subscription when considering all the heavy lifting it does. Finally, content research will always be free on Google, but a subscription to BuzzSumo can give you an edge in terms of current trends. For more information click here https://www.reddit.com/r/SEO/comments/f04tzl/pleasecritiquemyfreeseotoolstack/.