Where you should start depends on where you want to go with your guitar playing. What kinds of music do you like to play or listen to? (jazz, blues, rock, classical, death metal, etc) What do you want to be able to do? (site read a chart, improvise solos over chord progressions, play classical influenced melody lines, play cool chord progressions for someone else who is soloing, etc...) That will help you determine where to start.