it could be also interseting if they're an auto-upgrade, like we buy a x tier elixir, then he auto-buy the under-tier elixirs and ingredients (because the first red elixir get extremly low-price when we're close to get the 2nd one, but it take so much time to get all thing balanced when we upgrading the red-elixir-1).
little mistake (SPOILER WARNING): when we become alien and we go on earth, the planets description still in the earth to Kepler way (like earth have Kepler description and Kepler have earth description)
You can multi-buy by holding down shift and/or control. See the introductions panel next to the game for further instructions.