Since Google page 1 is your target destination and you are on page 15 for that keyword, you really only have 1 option and that is to outrank your competition. Sounds pretty basic and simple of an answer but it really could not be more simple. You have 14 other pages of competition to analyze so start there and ask yourself a few questions.
First question: Why does that website rank higher than mine for that particular keyword? Other questions: Do they have a better backlink structure? - You will need to analyze your competitor's website. Do they rank for other related keywords (as rownok mentioned)? - You will need to perform a full keyword analysis of your competition and look closely at relevant keywords related to your main keyword. What is the age of the competitor's domain and what is their domain authority? -If your competition is long established on the web you will need time to outrank.
If you have trained as well as more experienced runners train and have good form like they have, you can still win the race. Practice harder than they practice, train harder than they train, and run harder than they run and you'll win!