I used to have a running machine. I ran on my toes as well, it's way more bouncy & fun. & let's face it, if you're not having fun you're not going to want to exercise. Run however you want!! Who cares if you run like a fag, you're inside after all, no one can see you. Unless this is at the gym? I don't know why I'm assuming your friend owns a running machine..
Anyway, trainers a probably a good idea though.