Rest between sets of 1

I'm going through the handstand series trying to prove that i've mastered each movement before I move on so as of now I'm doing wp/pe3, fkp/pe3, and wr/pe4.  My problem is the sets of 1 are extremely easy.  This week I'm doing 5 sets of 1 rep.  How much rest should I have between each set?  I could easily do 1 set of 5 and be done with the entire thing, today I did.  Should I advance to the next block or stay the course?

If you can test through the mastery standard (that is both rep count and execution) then yes, you should move up on your next session

For the wrist exercises, be conservative when testing out.  For example, if you're able to do 5x5 of PE3 right off the bat but it's pretty challenging, don't jump to PE4.  Start at PE3 week 5 or week 9.  When you start doing these exercises a few times a week for a month, the volume can quickly exceed the recovery ability of the small wrist muscles and tendons.