So long as you're recovering gold, I'm not convinced there is such a thing as too diluted. It becomes clumsy to handle, but gold can be recovered from VERY dilute solutions with no issues of which I am aware. Same thing goes for silver, where it is cemented or precipitated as silver chloride.
As you become more comfortable with working with chemicals and the refining process, you'll learn to use only the amount of water that is necessary.
Platinum and palladium, on the other hand, will not respond to chemical precipitation when too dilute. They also rarely precipitate entirely, even from saturated solutions. When working with either of them, keep your solution very concentrated.
Harold