-Baselayers are designed to wick moisture away from skin, thus any kind of synthetic or wool blend are the popular choice. My favouriate is the Capilene line, but you can pick up inexpensive synthetic shirts from Goodwill or even Target for under $15-- it is good to have a couple in different weights for different weather.

-Midlayers are your insulations: popular choices include down and primaloft for their warmth to weight ratio. They are also more expensive ($120+). Other options include fleece-- available cheaply in practicly any store.

- Outerlayers-- protect from the rain. Marmot's Precip jacket is a great, affordable LW jacket. There is no need for a $200 rain coat. Rain pants are also worth considering if you live in a wet area. If not then regular hiking pants or nylon running shorts dry out quick enough to not warrent the need for them.

- Something else worth purchasing is a windshirt-- Golite Wisp, Marmot Ion etc etc. Worn over a baselayer to block the wind and you will be able to leave the rest of your gear in your pack. Wind pants are also nice to have-- they are usually DWR coated and are more breathable than rain pants.

If purchasing used, check the loft of the down, hold items of clothing up to the light and check for tiny holes. Rain gear and windshirts may need to be re-treated with a DWR coating.