I didn't use a quote in mine; it's a personal statement so really it's about you, and what you think, not somebody else. There's really no structure to follow but it's important you address a few things, mainly why you're applying for whatever course you're going for (develop this by talking about the subjects you're taking at the moment and what research you've done on the course), what personal qualities you have with some examples to show them, and any extra-curricular activities you have...
I don't think it's necessarily a bad idea to start it with a quote, it's a bit different and that may be an advantage, just make sure you do not stray too far from what it is you're meant to be saying.