Question on ranking top on google

I started a new fashion business lately and I am trying to choose the right keywords and strategy to boost ranking.

my first question is, there is so much competition on common keywords like "sunglasses" "jeans" etc. Should I not bother with keywords that have a lot of competition? and should I add more details to the keywords?

Second question, should I diversity the keywords when purchasing link building packages from different providers? Or should I submit the same keywords to all of…

Question on ranking top on google