In my experience it is fine to have only your given name on the ticket, as long as all names are included in the secure flight data. I have a first and second name, the second name is my "given" name (a concept that used to be quite common in Germany). I always book my tickets with my second name only and enter both names in the secure flight data, or have the airline enter it there. I travel to the US once or twice a year and have never had a problem. Even if you forget to enter one of your first/given names this can still be updated during check-in.