it really depends on a SaaS you provide, but all in all, there are some points that each SaaS site should have. It's definitely a landing page, well-structured site, call-to-action buttons, etc. To give you a better insight, I'll give you an example of the page that impressed me the most of all I found out there. It's https://www.paldesk.com/ for sure. Use them as a guide and I'm sure you'll do what it takes for a great website.
Good luck with creating and designing! Hope I helped you.