Well, the way I see it, it can't hurt to become a CNA first. You'll make more money as a CNA than you would in fast food, and if you want to be an LPN, being a CNA for a while is a GREAT idea. It lets you get used to working in a healthcare environment and will make you more comfortable doing patient care. I have found that CNAs tend to make the best nurses, because of the extra experience and the different perspective.
As for uniforms, wait until your class gives you a list of things you need. Some require a certain color or style of scrubs
, some don't. You probably won't need to wear them until your clinicals. Don't buy any supplies until you know what you need - I'd advise showing up with a pen, a pencil, a notebook, and a binder or folder until they tell you what to buy.
As the above poster mentioned, you will probably need a stethoscope and/or blood pressure cuff, but DO NOT buy one until you are told to, because some programs require a specific brand!
Good luck and let us know how things go.