The most effective ways to track fertile days that cost ZERO dollars is to:
Fertile mucous-eggwhite vaginal mucous that stretches up to 9cm on fertile days
Cervical position-up and open, the cervix will be deep in the vagina and have a slight opening you can feel with your fingertip(as opposed to when menstruation happens and the cervix is close to the vaginal opening)
BBT Charting-this is a great way to see if ovulation has happened and when. Must be done at the same time every day before getting out of bed.
BONUS:Then there is one more way which I use a lot for my clients which is the smiley face Ovulation test kits(not a cheap investment). They are by far the best ones and most reliable.
Happy baby making!!