I thought the recommended time between spots was like two weeks? Not sure but could have sworn I read that somewhere, but don't feel like trying to look it up right now.
Everyone seems to react different. My first quad shot I hit something, and it hurt like hell. But my first delt shot was smooth as butter. Tried quad again and barely felt it. Tri also went crazy first time. It was very swollen but tried again and nothing.
I'm deathly afraid of needles. You'll be fine, just keep poking yourself in different spots and see how many you like. You will probably be surprised at how quick your list builds up. Only spots that come to mind that I haven't tried are calves and bi. Technically traps as well, but I did put the needle all the way in but while it was just sitting there it was hurting. Figured screw that ish, if it's hurting just sitting in the muscle no way was I about to inject (yea I b****ed up).