Nienke, even if you don't go for "optimum" and just try to improve your SEO, you'll already be way ahead of most websites out there which don't even give SEO a second thought.

And as much as the OP was gently criticised as being outdated, the basics remain the basics and they still work.

You need good content.
You need to be aware of the keywords and phrases you are targetting.
You need to put those key words and phrases in the right places (domain name and page title are HUGEly important for this).
You need a short, attractive page description in your description META.
You need to get some exposure where there's already some traffic.

I'm not going to knock the rest because it all adds up, but I really think those are the most important basics without getting too tied up in subtleties.