You could process these boards several different ways but start with a small amount as a test until you get a proper technique figured out because if you end up making a mess a small mess is easier to fix than a huge mess.
First question:
Is there gold plating under the solder mask ?
If no then that will narrow down the process for you.
Second question :
Is there any solder or components on the boards?
If yes you need to remove everything you can as far as components, even little mlcc's.
If they have solder on the boards and you being new, then you should take the simplest route.
Before you start have all of the protective equipment to keep you safe like nitrile gloves, safety glasses ect., do this outdoors and where children and animals can not get ahold of it.
Do it where the wind blows the acid fumes away from you if you do not have a fume hood.
My opinion is that first you need to soak them in hydrochloric acid to remove as much solder possible if they do have solder.
Once you have the solder leached off and you rinse the boards very well you can go to the next step.
I would just put them directly into a large beaker with dilute nitric(50/50) to quickly remove the gold plating but if you are brand new to refining I would not recommend it because if you do this process wrong you will have a nasty tin nitrate in with your gold foils and it is a giant pain to deal with if you don't know how.
I think for you if brand new to working with acids you should just get a aquarium air bubbler and put the hose and bubbler stone in the bottom of a one gallon bucket, fill up the bucket with boards maybe to about the half gallon point and then pour in enough hydrochloric acid to cover the boards about a inch or two over the boards.
You can drill a hole into the bucket lid that's the same size or a little bit smaller than the hose so the hose fits through but the fumes from the acid will not escape, give yourself plenty of hose inside the bucket to open the lid without pulling the bubbler stone out of the bottom of the bucket.
Your aquarium air pump can sit on top of the bucket lid and you can pull off the hose when you want to open up the bucket to check on the progress.
The hydrochloric acid will start turning green from copper going into solution, this copper is copper chloride and is what will be doing the work of dissolving the base metals that the gold plating is plated to and the oxygen from the aquarium pump is what will help the process along.
Without the air bubbler it will take forever but will get your gold foils released.
When the acid is almost black in color you need to pour out about 9/10th's of the acid and replace it with new acid.
You can process several boards with the same solution, just remove the boards that have the gold plating stripped and rinsed off, then put in more boards.
Once you decide to stop the process you can remove and rinse the boards, filter out the gold foils, wash them well with water and refine them with aqua regia or the hydrochloric and bleach method.
Before you start anything search the forum and study all of the steps including dealing with the waste.
Become very familiar and confident about the whole process long before you start and it will go smoothly.
It is not a fast process but it is simple, cheap, and effective.
For us who are very experienced refining and handling all of the chemicals and chemistry, we may use other methods that are faster but more dangerous.
There's several routes that you can go but start small and keep it simple !!!!
Other forum members will chime in and probably add to what I have said or maybe even give you a different process that they think will be a better fit for you, seriously consider the methods that are given and decide which one works best for you.