What's your experience in running paid ads?

I have a success story. But first, some math.

Your CAC ($) = CPC ($) / CR (%)

Let's assume CPC (Cost Per Click) = 1$.

You want your CAC Payback Period to be less than 12 months.
How much is your yearly subscription value?

Ideal scenario:
CAC < Yearly Subscription

What is your CR - conversion from new website visitor to Subscription?
10%: CAC = 1$ / 0.1 = 10$ ; amazing
1%: CAC = 1/ 0.01 = 100$; very good
0.1%; CAC = 1/ 0.001 = 1000$; pricey

At first, we had high CPC and low CR, which were too expensive. We had just the search ads because they needed no images/videos.
Limiting CPC helped a bit. Affordable traffic enabled us to improve the website and CR.
Then we started to optimize Ads to CPA be lower than a threshold.
Remarketing with lovely creatives + Automatically Optimized Audience did the trick.

Now we have 4$ per registration, with 0.2$ average CPC and 5% CR. Best campaigns had up to 15% conversion. Some rare campaigns are even better, just the volume is minimal. For example, there's a campaign with 8 regs out of 17 clicks for almost no money.

Our CR of 5% is only to a free tier, not to paying subscribers. So we work on better onboarding to increase our activation. Then retention of free users. Then conversion to subscribers. Then retention of subscribers.

It's a long journey. What makes us happy and motivated is our Discord channel #customers. Registrations keep coming. They start to invite friends and activate.
For the first time in my life, I see exponential growth curves. The amount of user feedback = tasks for devs grows as well. But those are great challenges to solve.

And yes, we spend 100$ a day on ads => 25 new regs daily.

About attribution - the last click is fine for now. Keeping it simple.

My experience is that you have to spend a lot of money to test a lot of targeting hypotheses first. Or have a lot of experience with testing. Or pay someone who has a lot of experience.

And only after testing a lot of hypotheses, find a channel where the ROI is acceptable.

I have nothing against paid media, but I advise on some other stuff before going that route

I am not sure about your question on attribution. Are you asking about which model to choose (depends on your situation) or something else? Attribution should be relatively easy to tract (if you have a modern analytics solution embedded) once you have your model (thanks to UTM).

interested