As you clip you'll develop your own personal style, and have a preference of blades. Different people use different blades. I personally hate a #10, but its a good blade for people just starting out. I use mediums, super blocking's, x-block's, and a 5/16". I start out with a medium to shave their head, throat, brisket, and tail. Depending on what kind of hair they have I may or may not go over their neck with a 5/16. If its stringy and unworkable I'll go over it, but if its fuzzy and you can work with it I'll free hand it. After I get the shaving out of the way I switch over to my super blocking blades and don't stop until I'm done. With a super blocking if you touch it, it cuts it. There's not a lot of room for error, and I would recommend a medium in lieu of a super blocking if your just starting out. The only time I use an x-block is when I'm clipping something with glue.
I would recommend buying two of whatever you buy. That way you can continuously swap them out without them getting too hot. I have two mediums, two super blocking's, two x-blocks, and one 5/16" because it never gets used enough to get too hot. It's not the ultimate setup, but its perfect for what I do clipping only clean show cattle.
Above all else, take care of your blades. I would recommend three things, Andis 5 in 1 cool care, some kind of clipper oil, and a small brush. Use the andis while your clipping to keep your blades running smoothly, when your done brush your blades off hit them with some 5 in 1(prevents rust) and store them, and oil & clean your blades and clippers regularly.
