i like the internet cheapies too, like wondfos, you can get them from ebay or amazon.com, etc. they work great and they are like .30 each.
i have lots of advice! there's a fine line between loving them and hating opks- i think it depends on if you use them the best way possible. i love them. so for starters, the key to reading them is to hold them at arm's length- when they are positive, they are obviously positive, you dont have to look closely at them, that's one of the reasons some people get confused, they overthink it.
you will want to test 2-3 times a day, one of those times ideally should be around 2 pm. i start on the first day of fertile cm, that works for me. you can look at my chart and see what i mean. plan to start at least probably 5 days before you expect to o if you dont have a lot of cm. when i am expecting it to go pos, i will test at maybe 11 am, 2 pm, and then maybe 6 pm. once it goes positive, i test once a day at 2 pm, but that's up to you. (what i used to do is keep testing on the same schedule and then just chart the trend- what i mean is... if a got a negative in the am, then a pos in the pm, i would chart positive, because it was trending positive, if the next day i got a pos in the morning and a neg in the afternoon, i would chart it for the day as neg, because it was trending neg. i know others who do it this way too, but now once i get a pos, i just test at 2pm once/day. whatever works for you, as long as you are consistent.)
now, here's what else i recommend. say you get your pos opk, then it goes neg sometime the next day for example. ok, once it's neg, keep testing, once a day, until you get your crosshairs (or you are really confident that you temp is up and you o'd.) it's just another day or two, and i have seen too many scenarios where this wasnt done and there ended up being ambiguity, so i say, just do it. some people say after you get 1 pos, stop testing, but i do not recommend that strategy at all. a pos opk, you have to remember, does not guarantee an o. it means you are having an lh surge, and that should trigger an o, but it's not a sure thing. you have to keep watching.
and just remember, you can o anytime from the day of your first opk until 48 hours after your last. the avg is 36 hours after the first.
there's more, but that's a good start. good luck!!!