All the major manufacturers make gold machines. Whites makes goldmaster, Fisher makes Gold Bug, Tesoro makes the Lobo super trac, Garrett makes the Scorpion and the stinger.
Minelab makes some great gold detectors for heavy mineralized ground, but they are pricey.
All of the above are good machines. Check into clubs in the area you want to search in, the members will have a pretty good idea of which machines will work best in their ground. Then take a look at ebay for a deal, or pay a little more from the manufacturer for great support and warranty after the sale. Kellyco is a sponsor for this site, and they usually have good prices too.