It can be tough to get gold in the begining, but once you get the first few items and with Ashe's hawkshot ability you gain gold quite quickly. That being said, I normally finish the game half way through building the fifth item, though have finished the set on a 36/6/16 game that lasted over an hour. Other things if you are worried about gold would be to change your skill tree to grab Hawkshot even earlier in the game gaining an additional 5 gold per mino kill.

good luck getting 18-19k gold for the items in this build... ya its possible, but not going to happen often.