Ovulation guidance!

Help me please, I am currently on cycle day 6, this is the first day after my period has finished. When do I start to test with ovulation tests? Last month I think I totally missed my mark by a whole week! My period was 4 days late and my cycle can go from 28 to 35 days each month. So I think Glow’s calendar prediction was off ☹️. when to start testing?? I have a friend that says she ovulates right after her period. And I haven’t even bought the tests yet! Going tomorrow.