Welcome to the Make community!
While this is a good idea, technically this doesn’t exactly schedule the scenario for first Monday of the month, but for all Mondays in the month, with a filter to only run the rest of the scenario if it’s the first Monday.
So it can cost a minimum of five operations a month.
It would be nice to have Make build this directly into the scheduling system itself, to be able to select “1st <weekday:Monday> of the month”, “3rd <weekday:Monday> of the month”, etc.
You can submit this suggestion to the Idea exchange, under Platform ideas and improvements.
Don’t forget to search for it first, just in case someone already suggested it, so that you don’t end up creating a duplicate.
In the meantime, I’ll show you my way of only using one operation without requiring any filters:
[Showcase] How to schedule scenario for first Monday next month – #1 samliew