Manticore settings for a known goldfield

Start at low to medium, raise it only while the machine stays quiet and work from there. The rule that matters more than the number is that a machine running so hot it chatters is a machine that is hiding faint deep signals in its own noise. Turn it up until it becomes unstable, then come back down a step, and re-check whenever the ground changes.

Yes. High frequency and a small coil are what make sub-gram nuggets audible, and heavily mineralised ground is exactly where careful ground balancing earns its keep. Expect to ground balance often as you move across the ground. The settings above are a starting point rather than a prescription, and the work worth doing is calibrating them against buried known targets in your own soil.

Small, and high frequency if the machine offers a choice. Coil choice changes target separation more than any menu setting, so it is the first thing to reconsider when a site is not producing. Coils are machine-specific and often series-specific, so check the compatibility chart for your own detector before ordering, because a coil that does not fit is an expensive mistake.

Not a factor on dry ground. For reference the Manticore is rated to 16 ft. This is the one specification on the page that is absolute: sensitivity and discrimination are preferences you can experiment with, and a waterproof rating is not. A waterproof searchcoil and a fully submersible machine are different things, and confusing them is how control boxes die.

Almost certainly, and you should assume yes. Get the landowner's permission before detecting on any ground you do not own, in writing where you can. Many public parks and recreation grounds prohibit detecting outright, national parks and protected archaeological sites are off limits in most jurisdictions, and the rules vary by country, state, county and individual parcel. Check before you go.