This question is quite broad. To help you better, a bit more of information would be helpful:
Do you have any general programming experience? Do you know C++ (which is the programming language JUCE uses)?
Did you already try anything or are you only looking for tutorials at the moment? If you already tried to build a plugin, what was successful, where did you run into problems?
Regarding the plugin that you described, do I get it right that this should be an instrument plugin, e.g. one that only outputs a signal but does not process an incoming signal? What’s the use-case of it? Sounds a bit unusual at first and unusual things might not be the most straightforward kind of project when you are just getting started.
You mentioned VST. Are you aware that you are no longer allowed to build VST plugins if you didn’t sign a contract with Steinberg years ago and therefore the SDK to build a VST is no longer included in JUCE? Good news: Building the modern VST3 format is no problem though
it’s best to only come here for a very specific question. for example if you already have a working project and then ask yourself “how to load a wav file?” or so.
what pp said about vst no longer being supported might be a little ambiguous. i would consider vst3 the current state of vst