OPK questions

Brittany • 🍳 Wife and mama to two beautiful girls and three angel babies. Currently pregnant with surprise baby #3! Adventure seeker, foodie, wedding photographer, sushi enthusiast, former DJ, avid reader and avoider of Indian food.

Ok, it's time for me to get serious here. What kind of OPKs are the best and why? I feel like they're kind of expensive. How many do you go through in a month? Do you start testing right after your period? Thanks in advance for any advice!