For a beginner this is a confusing and sometimes difficult question.
The first thing I will ask you when you tell me “I’ve never done it but always wanted to” is “Do you want to look for gold or coins/treasure?” Most people want to look for gold so let’s take a look at the choices you may have.
Firstly let’s look at the types of detectors in general terms.
VLF- Stands for Very Low Frequency and is the technology platform that this type of detector runs on. VLF machines are usually the cheaper option but are restricted in depth especially as the ground mineralisation increases and this can make them difficult to use unless the sensitivity is decreased accordingly, resulting in performance loss. The upside is that this platform usually has some sort of fairly reliable discriminator, which can be used to accept or reject selected targets. These detectors make excellent coin/treasure machines and are widely used for this purpose. There are some dual-purpose machines available in this platform to be used for coins/treasure and also gold prospecting but the latter is usually a compromise on performance. These detectors start at around $199.00 and run up to around $2700.00 for a top of the line machine. Dual purpose detectors are in the $750.00 to $1300.00 bracket.
PI – Pulse induction is the platform that historically offers the best performance and ground handling capabilities. These machines are the most expensive, but also the better performers, if we don’t include the GPZ7000 (which isn’t a PI machine). Cost for these detectors is in the $3800.00 to $6000.00 range and offer excellent performance especially in mineralised ground and up twice the depth or more against a VLF machine in this environment. Discrimination is available on some models but isn’t as reliable as the VLF type from my experience, and is something that I do not use at all when searching for gold. Interestingly one of the better beginner gold prospecting detectors, the SDC2300, has no discrimination at all and I believe that is a good thing.
GPZ7000 – This detector is somewhat of a hybrid utilising ZVT (Zero Voltage Transmission) and is probably more closely related to the VLF machines, but is a very special case. Where VLF detectors constantly transmit and receive, they can “liven” the ground up considerably making the coils magnetic field difficult to penetrate the ground as deeply. The GPZ7000 rapidly switches coil current flow direction and avoids this problem. This detector is arguably the best for all round performance and even though it has a lot of settings and choices, people generally are not changing them constantly like they do on some of the other models.
The best advice I can give to a beginner is “Buy the best detector you can afford if you are serious about detecting”.