I receive this question each time I talk to owners who have a revenue from $500k to $5M.
Here is the simplest answer that I give them (and the exact order that I have used in each of my seven-figure projects):
In case you are not aware if people will pay for your product → just start with ads.
There is no other quicker way to find out the truth than doing ads. For 60–90 days I will do a little controlled spend on Google/Facebook and watch the results. The very moment when I see the 4–5× ROAS, that is when I understand that the market exists and that I am not making a guess.
The day when ads start to be profitable → take that profit and invest in SEO.
That means that today every ad dollar can be used for two different purposes: to get cash today and to get free traffic tomorrow. The flywheel is the way you go from struggling to be on top of the organic rankings without asking for the algorithm gods' help.
B2B marketplaces (Amazon, dealer networks, etc.) should be your last option.
They are your killers of margins until you have the strength of a brand and customers waiting for you. I never use them until the moment when I can set the price instead of racing to get the lowest one.
A quick rule I share with every owner:
Under $500k → 80% ads, 20% SEO, 0% marketplaces
$500k–$2M → 50/40/10 split
More than $2M → reverse it: mostly SEO + owned audience, ads for spikes, marketplaces only for overflow
If you use that sequence, you will never spend half a million dollars on figuring out what actually works when doing your business. I have done it from scratch numerous times — it is not exciting, but it has never left me without success even once.