G'day Scott.
The Ace 250 is not designed to find gold due to it having a fixed ground balance. I have seen a case where gold has been found with an Ace, however in the case in particular, the gold was picked up with a top end gold machine that couldn't properly locate the target; the Ace found it straight away.
If you are looking for an affordable gold hunting machine, then you will be looking at a VLF machine. It depends on what your budget is.
The Minelabs PI machines although very good at gold hunting, are cost prohibiting, however, the Garrett Infinium does very well and less than half the price.
Most detectors with an adjustable ground balance, will do OK for gold hunting, some will do it better than others though, and it will depend what you are looking for in a machine. I personally have no experience at gold hunting, but there are a couple of folks on this forum that do. They don't come on all the time, but if they do, hopefully they can give you some more input. You will need to give some more information though, so that we can help you with a greater degree of intelligence.
Mick Evans.