The material definitely makes a difference in the sound. Usually light colours (silver, nickel) make for a brighter sound whereas dark colours make for a darker and richer sound (24k gold, black nickel). My friend has a flute which uses a gold head piece (if that's what they're called) and a silver body. My saxophone is 24K gold with a wide bore so it produces a dark, expansive sound.
If you are just starting to play, I would recommend something like an entry level Yamaha flute. Choose a reputable brand from a local dealer if possible. It may cost a bit more, but usually they will be able to provide service and tune-ups (unless you know a technician). Reputable brands are better for entry-level instruments as they have consistent build quality at a reasonable price. Going all out isn't quite worth it yet, because the instrument is only half the sound; the rest still depends on the player. Once you feel that you have developed a good sound and decide that you really want to continue, it is a good choice to invest in a fine instrument.