This advice is for people who want to promote their product or startup with organic traffic and are willing to put in the work. This is what has worked for me, more than any hack or shortcut I have tried.
Do not write random content. Write around keywords where you have a shot to compete. If you are just starting out, look for long-tail keywords that are not too competitive and are likely to convert.
Write useful and high quality content for your audience. The kind of content that people search for and want to read. Cover your topic in depth. Use a content optimization tool.
Add Google Search Console to your website and keep a close eye on which keywords you are getting impressions for. You'll discover new keywords that your content is already ranking for. Start targeting them with new content or by updating your existing pages.
Content marketing takes time. If you are going to do this, take a long-term approach. It will take months before you see significant results.
If you do any of the following things, you are probably procrastinating or wasting money
Pretty much all the information you'll ever need about SEO is available for free on the web. Plus, people selling you stuff are incentivized to add unnecessary complexity (to make it worth your money.)
Vetting good writers is difficult and time-consuming. They are also expensive. If you are just starting out, you probably do not have the time and the money to do it right.
Backlinks offered by link farms are of very low quality and do more harm than good. Do not waste your money on them.
I think this point speaks for itself.
A lot of people try to make SEO sound complicated. I think SEO is simple to learn but difficult to execute and wanted to have a website I could refer people to.