OKP tests???

Mandi • Married to my best, I'm Parapeligic, 30!!!! I have 16 angel babies in heaven! Trying for my first full term pregnancy. 🙏 for a miracle!! God Bless!!!
Where is the cheapest place to buy OKP tests at and how many should I buy just to make sure I don't miss my ovulation window? Thanks in advance! God Bless and good luck to all TTC!!!