PPC ads to get paid signups?

So I am in need of getting Pay-Per-Sale signups because I am generating too many free leads and no sales. Thinking of investing money into PPC ads to try and get sales, don't care if I lose money because I just need to generate some sales. Any advice? And what kind of PPS/PPL ratio is normal for credit card signups?

Ratio differs from offer to offer. You need to test your offers.

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Generell ratio is 3-7% sometimes higher.

We are getting 5-9% sometimes 10%.