That's a good price. I start using mine around cd9 (or sometimes a bit sooner) because I've O'd as early as cd9 in the past. But if you O later in your cycle then don't use them that soon. IF you know your bodies "cues" to gearing up to O then that's when to start using them. Like I'll get almost like AF symptoms then I'll O about 2-3 days later so that's when I start. AS far as what time. I've used them at 12noon, 2p, and later. But no earlier than noon. I use one a day until my line starts to get darker, then I'll use 2 a day till I get my + They say once you get your + u can stop using them, but I've con't before and I'll get 2 or 3 days of +
Good Luck hun. The first month I used them I got discouraged because mine were - and I quit using them, the second month I was headstrong and just kept using them and got my + and been using them since.
Oh and no u won't always get a line if you aren't anywhere near O. So say you use one today and no line you could probably wait a few days to use another. But as soon as you see the line then use them daily cause your + is coming if you are going to O.
I hope this response helped.

PM me if you have any questions.