How to get the best ranking improvement from SEO work
I'm working to improve the ranking of a site for a list of keywords.
I know I have to work in internal links, external links, content quality, content quantity, correct use of keywords, penalization checks, and so on.
How can I know in which of these areas I should give priority at a certain moment?
Are there tools that suggest which is the area I should work at this moment to get the best ranking improvement?
Thank you for your help.