My advice would be to make use of pre-launch platforms such as https://microlaunch.net or product hunt and other organic ways to gain traffic. Meanwhile, make sure your funnels converts, then think about Ads later on.

There is no solution that fits all. Depends of your target audience and where they operate.

Audience is on Twitter/X ? Build in public and post regularly about your work. Audience is on facebook ? Targeted Ads may work for you Audience is a set of professionals ? Target forum or places they go

Disclaimer: I'm not an expert in marketing either :)

Reddit is a really great way right now, due to the boost to Reddits rankings on Google you can find old Reddit threads that still allow comments in the top 5 on Google with very high traffic keywords.

Newsletters and directories like https://microstartups.co/

Invest in SEO.

Maybe too abstract, so here is a piece of actionable advice:

99% of SEO is to publish interesting content for your target audience.

Read Alex Hormozi's "$100m Leads"

It depends on what your software does. What it does?

My goal is to create micro SaaS with unique functionality under the name of my organization and following its niche, i.e. web and software development. So our paid software will surely allow cloud/AI services or even project organization for freelancer/startup.

This is incredibly generic. Too generic to:

a) help you build anything useful

b) craft a value prop that any customer would find compelling

c) help the users here give you any real advice.

1. Get really clear on your ICP first https://salesroads.com/tactics/icp-sales/

2. Be able to answer “why you” if your market is too generic you likely don’t have a strong story here. Why is this the most important thing to build right now for your customers and why are you uniquely suited to building it?

Project management is an incredibly crowded space and software devs are one of the hardest-to-reach markets.

I'd consider another niche that you can reach with ads or that is more likely to be receptive to outbound.

This doesn't mean anything, this could cover most SaaS businesses. Sounds like you have (the idea of) a solution looking for a problem.

Talk to users.

Billboard in SF just like the rest

Talking to potential customers one at a time is the simplest thing that might work. And it will be work. Hard work. If you don't want that hard work, don't have customers.

Talking to customers one at a time is hard to scale and it is easy to scale zero customers. This mostly makes solutions that scale attractive when starting out. Scaling when you have many customers is hard work. Harder work than talking to customers one at a time.

Good luck.