First up a powder brush. I use my powder brush to apply a powder foundation. I personally use MAC Studio Fix foundation and it can tend to look very heavy if you use the sponge applicator. So I take my large powder brush and apply it to my entire face.
Next a blush brush. The difference between a blush and powder brush is that a blush brush has a more fanned appearance. This allows your blush to go on with a more natural look. You don't want to be walking around looking like a clown with big circles of blush. You can also use this brush for bronzer.
The last brush I recommend is a brow comb. Sometimes eyebrows do not want to do what they are supposed to. Use this comb to get them where they are supposed to be. Most brow combs have two sides. One is more brush like and is used for taming brows. The other is like a small comb, this side can be used for removing clumps from your mascara or also used on your brows as well.
Ok now that you know what brushes you need, where should you buy them. Brushes can vary widely in price. Some high end brushes can run as much as $80-100 a piece. If you have that to spend, then one brand I would recommend is Trish McEvoy. They are great brushes but are definitely an investment. Another brand that I like that are pretty reasonable is Sephora's brand of brushes. I have a few of these that I use my self and I have been very pleased with their quality. If you don't have much to spend you can always go to the drugstore or even Ebay has brush sets for as low as $10. Even if you don't have the very best brushes you will still get a much better result than using the applicators that come with the product.