A lightweight pair with a sturdy sole will do nicely. Blisters can ruin any hike, so be sure to break in your boots before you hit the trail. A T-shirt layered with a cotton shirt that buttons gives you lots of temperature regulating possibilities. Shorts are useful much of the year in Southern California, but for cooler days and walking through brush, a sturdy pair of long pants is necessary. Hats help prevent sunburns on your face and scalp as well as protect against heat loss when it's cold.
Sunglasses are essential when walking over snow or on hot, exposed slopes.
Make sure you buy a pair that provides adequate UV protection. As for rainwear, an inexpensive, water-resistant jacket is okay unless you walk through brush. Some of the new breathable, high-tech fabric laminates are superb, but expensive. They could serve you well, though, if you hike a lot. But the day you hike is not the day to diet.