I am a groomer and agree with Kirty, Wahl Single speed are my favourites and they are the brand we use at work. They don't get as hot and are not as heavy to hold as some of the other brands. Whatever you purchase the faster the clippers the better the cut. Look around because you can sometimes get clippers on special - now may not be the best time to purchase as they are in hot demand with the weather warming up.
I agree that by purchasing your own clippers and blades you will improve with time and save yourself alot of money. The general guide for blades is the higher the number the shorter the cut - a 40/30 are surgical blades, 15/10 is close cut (for bottom and groin), 7 is usually seen on a clipped cockerspaniel and a 5 on the maltese x/small breed dogs. A 4 for the owner that does not want a short cut - again this is only a guide line and differs in different salons and on different breeds of dogs. Get yourself a slicker brush and a good pair of scissors. Unless the coat is matted or extremely course avoid skip tooth blades as there is more chance of cutting your dog. Your biggest hiccup will be whether your dog is going to be a good client or not!!!!
I would never discourage you from having a go at clipping your dog but please be careful. Working in the grooming industry we hear and see heaps of horror stories of dogs being injured, cut and/or people being bitten. Best case scenario would be if someone could teach you - do you have any vet nurse friends or know of a breeder that would help? I would get on the phone and make a few calls. Most people that work with animals would be happy to teach you.
Finally if you take the plunge be prepared for a mess - wear denim shorts/pants (hair does not stick and will come out in the wash, closed shoes (in case you drop something), no jewellery that can get caught and finally (I now this from experience) don't groom with your mouth open. Nothing like dog fur for lunch!!!!