Gold is just the name of the weave - aka the same Gold weave used on furniture.
A well made single weave, properly cared for etc will last you many years (I had two Torah single weaves that lasted about 2-3 years apiece).
Single vs. Double differences relate to long-term durability and weight.
If you're new to the game, look for a bargin first time around, see whether you like the sport or not, then aquire additional gi's when other specials happen your way. If you stick with the big brand names (that other people in your club are also happy with) you cannot really go wrong. I often liken the process to buying a new pair of runners: not until you try a few brands yourself will you know what's right for you.