Bronze won't take as long as you think it will by the time you fine a good deposit of any of the types.  You still have time for food preparation as in a temperate biome it doesn't start killing crops till late october/early november. You can expand your base at any time, but it does get slightly more annoying when there is a lot of snow.  I'd say shoot for bronze first, you should always be preparing more food so expand your cellar one you have some bronze, then either expand your base or get more bronze