Should a solo founder run paid ads?
Short answer
Not until organic conversion is proven. Paid traffic amplifies whatever your page already does — if 100 free visitors produce no signups, 1,000 paid ones will produce no signups and an invoice. Ads are a scaling tool for a funnel that already works, not a discovery tool for one that doesn't. The exception is spending a small fixed sum purely to buy traffic quickly for a conversion test.
The longer version
Not until you know that organic traffic converts. Paid traffic is a multiplier on the page you already have. If a hundred visitors arriving for free produce no signups, a thousand arriving at £2 each will produce no signups and a bill for two thousand pounds. The ads are not the problem in that scenario and no amount of tuning them will fix it.
There is a genuine exception, and it is worth knowing. If you have a page and no way to get traffic to it, a small fixed sum — a couple of hundred pounds, capped — spent purely to buy a few hundred visitors quickly is a legitimate way to run a conversion test. You are not buying growth, you are buying a faster answer to a question. Decide the number before you start and stop when you hit it.
Once conversion is proven and you know what a customer is worth, ads become a straightforward arithmetic problem rather than a gamble. That is the point at which they are worth real money and real attention.
The full argument, with the rest of the picture around it:
Every Way to Promote a Product, and Why Developers Get Each One Wrong