Honestly, run a lifetime deal on AppSumo; if you have some runway, instead of paying upfront for ads per se, you get an inflow of capital and a lifetime of support from customers who have some skin in the game. Next your sumolings who love your product will scream from the mountain tops for you, and referr you to other custoemrs launching your MRR
I’d go with listing my SaaS on an affiliate marketplace. It seems like a great way to tap into an established audience and leverage affiliates for growth!