OPK recommendations

Gina
I've been using the first response non-digital OPK. I only have one left so I was wondering if anyone found others that were better.
​My manager told me they used the 
Clearblue Fertility Monitor based on recommendations from friends who had success. It worked right away for them. I told DH about it but he said that's a lot of money to spend ($150-$200) and that it will happen when it's supposed to.