Selected answers from the Dumb SEO Questions Facebook & G+ community.
Dave Elliott: classic seo answer of it depends! If your site is authoritative on the subject then no level of competition should scare you. If you are quite a small and new site then almost anything could be a challenge.
Khurram Aziz: check how much Google is charging for adwords.. normally is a good guide
What diffculty score could be considered as low and medium competitive keyword according to semrush? 
