The best you'll be able to do is 5 mith plates, you need your 3 inv spots for cash, nats, and a hammer. The blast furnace is probably faster if you have people there to run it, and don't mind spending lots on money unnoting coal. The ore seller there will be out of coal if there are other people working the furnace, so bringing your own noted is a must. However, this is extremely expensive and you are very unlikely to have 2-3 other people in the furnace with you for an extended period of time. So gold ore is definitely faster, although you can get upwards of 100k smithing exp per hour if there are people working the furnace for you, even if you just use iron.