Hi, in general, having a proper DOM structure, alt attributes for images, and meta information (meta titles and meta descriptions) are the most important aspects. There’s a lot to consider when it comes to SEO, but I believe SEO is crucial when it comes to the fundamental basics—advanced SEO, in my opinion, is overrated. I worked in the industry for several years. Nowadays, paid advertising on Google is what really matters. Anyway, you can start here:
https://developers.google.com/search/docs/fundamentals/seo-starter-guide