I haven't read ahead, and someone may have already answered this, but I get these:
Amazon.com: Combo Pack 40 (LH) Ovulation Tests + 10 (HCG) Pregnancy Test Strips: Health & Personal Care You can't beat this anywhere, and I've been ttc a LONG time and used many many tests! 40opks and 10hpts for only $10, and the hpts are super sensitive and good for early testing.
About when to test....this is my theory/opinion: if you don't get upset with bfns, I think the earliest should be 10dpo. I wait till 12dpo myself, because I'll have AF on 13/14dpo, and most likely would get a + by then. Some months I just wait for AF because it's too depressing to see those stark white tests over and over, LOL. So, I say 10dpo at the earliest, but the longer you wait, the more definitive of a bfp you will get (ie, no squinters).
And about the lines- in most cases, they will not get darker in a matter of a few days. I took one at 12dpo and then another two weeks later and it was much darker, but that was 2 weeks later of hcg. So don't fret about lines not getting darkers, ladies!!!! You'll just stress yourself out.
Good luck everyone!