A couple of considerations: All Metal Detectors will detect gold but it really comes down to the size it will pick up on and at what depth. If you are going to be detecting creeks you might want to look at something with a submersible searchcoil at a minimum, a fully submersible detector would be recommended but not 100% necessary.
The difference between a gold and coin detector will vary, so you're not going to find a single machine that does both extremely well. For example the ground composition commonly found in gold bearing areas can be quite mineralised and will send most coin and relic detectors crazy. For these areas you will need something that can handle the mineralisation such as a PI detector, these are generally not cheap though. If you are looking to buy a "budget" detector you will most likely be buying a VLF machine which is an older but proven technology (as is PI).
With the above in mind and without knowing your exact budget I recommend a Garrett Ace 250, these cost around $300 (brand new), if you are buying second hand you might be able to get something a little better but for the price you can't go past it. The Ace 250 discriminates very well and has decent depth penetration, these are a popular choice for coin shooters on a budget and I know guys how own top end detectors still using these as a primary machine when coin and relic detecting.
Just don't by one of those GC / Snoop Finder detectors on Ebay, you will be very disappointed if you do.
P.S. Dont expect to pay for the detector on your first outing as suggested, it's not going to happen ;p
Cheers,
Squiggles
