Beings as it gets a bit warm down here in summer, I prefer a decent pair of shorts and a t-shirt in summer. In winter its a pair of combat pants and a t-shirt. Anything with lots of pockets to keep all the junk in. For long flights, Ive found a pair of lose flight coveralls to be the most comfortable.
I still have'nt found something to wear that stops me sweating though, as my instructor said - "they don't call it the hot seat for nothing"