I posted this elsewhere for someone else, clothing required, roughly in this order of importance:
1. Shorts/longs X2 with chamois insert. Adds to your comfort hugely. You need two if you end up going out a lot because you shouldn't wear them more than once without washing them, even on short trips.
2. Mitts - likewise. Cushions your hands on the bike, has towelling to wipe the sweaty brow/nose and protects your hands if you fall.
3. Shades. They're not to look cool, they're eye protection. Nothing worse than a bug hitting your eye when you're hurtling downhill at 30mph. Also stops your eyes tearing up on downhills. Also look cool.
4. Shoes. SPD types for clipless pedals. Stiff soles make for better pedalling. Normal trainers are too soft and your feet will likely chaff/hurt. SPD pedals have probably been the best invention for the bike in the last 3-40 years.
5. Wind or waterproof top. With back pockets.
6. Normal cycling top, with back pockets for the sunny days.
edit: oh - forgot. Helmet if you wish, though the choice of wearing one is yours.
Brand wise - again, the choice is yours. Depends what feels right and fits properly.