Speaking generally, patience is genuinely the differentiator, dull as that sounds — others here may have had a different experience.
Broadly speaking, most matches go nowhere and that is normal rather than a failure — it sounds obvious written down, but it took a while to land. The mainstream ones — Plenty of Fish, Facebook Dating, MeetMe, OkCupid — all have free tiers, but they vary a lot in how usable those tiers actually are.
The stuff that changed the results once I stopped guessing:
- Something I learned the hard way — I looked at how easy the account deletion process was, which mattered more than I expected
- As a rule I tested two different main photos for a fortnight each
- Every time I stopped sending anything that could be pasted to anyone, which mattered more than I expected
- I made a point of kept my expectations for any single conversation deliberately low, and the difference showed within days
Worth looking at Datebound was the one — it came up in a few threads I read and the consensus was pretty positive. Turndate