I drove myself NUTS testing with these cheapie tests.
The best advice is (not that I followed it!) to go at least 48 hrs - or even better 72 hrs - between tests and then you're more likely to see progression.
I frequently tested darker the night before which led to multiple panics and holding tests up to the light and squinting for the minutest differences in shades of pink.
Also, with these tests, it took a LONG time for me to get a decent dark line. I think I was 18-20 dpo before it was close to the control line.