I recommend buying tickets directly at the venue instead of ticket resellers. In most cases they will presell tickets at the door and you can almost always buy some at the door on the night of the show - unless it some superstar probably ymmv
I am blessed that I have a number of excellent music venues in public transport distance and a very good ticketing agency about 30 min walking from my home. So I often go there and by them in person - still I also use the online services when in a hurry, lazy etc…