Brass needs to be pickled with 50% Hydrogen Peroxide (available at the chemist) and 50% Vinegar. Will turn the brass to gold, well, look like anyway.
Bronze as Hookline said has many compositions, I just stayed clear of it because I did'nt know what it was made up from.
My friend uses a brass 1" Gate valve and brass connections for the condensers and were OK after he pickled them. He bought a cheap lead tester from the chemist here in the UK and it showed the distillate to be lead free.
I went the stainless steel route with the valves. As Hookline said in a previous post,'There a bit more expensive, but will last a lifetime'.
Looks like the other members have answered your materials questions thoroughly... I'll add plastics and rubber as materials to keep out of your stills vapor path...
Stop by the Welcome Center and give a proper introduction including any beer and/or wine brewing experience... Also checkout the New distiller reading Lounge...
Copper and Stainless are proven materials that don't have the same concerns/risks associated with it. While there may be isolated examples of certain materials working ok, or being safe under certain conditions..there are potential risks/dangers if you "don't" choose the right materials/conditions,etc. for these materials — and this can be an especially dodgy road to walk for those just starting out. That's why the normal recommendation is just to use stainless/copper for everything. It's readily available, it's easy to find safe materials to work from that you know will be safe to use. That's worth the extra cost...whatever that is...compared to the other materials.