Your experience with marketing your SaaS

I am building a SaaS tool and I have a marketing co founder as well however I want to ask you guys what are the best sources of traffic at the start of your SaaS? What was your marketing strategy with your SaaS? If possible then please state your ROI and capital distribution on which platforms (eg reddit,Facebook, Google ads) and what worked best for you. I know the metrics can be widely different and even negative for me but I just want to know about your experiences in it.