Google Adwords is an entire marketing game, that is why most people in adult fail, since they have not learned to market anything because the traffic has always been there, so I recomend you to start with this guy:
https://www.perrymarshall.com/google/
Really good markeitng advice focused on adwords, you dont need to buy anything if you dont want to (even I would recomend you to do so) but just by really studying his material you will be ahead of the rest.