You could ovulate at any time, so you can start using ovulation tests but they will work out quite expensive if you don't ovulate for a while. The TTC forum will have more advice. It can take ages to ovulate after you stop the pill/have a coil removed, or it can happen quite quickly. There's no way of knowing.
I didn't have my first period until more than 60 days after I stopped the progestogen only pill, but my cycles became regular after that. If you don't mind the expense, you can start testing anytime. But as someone who is pregnant I would say it's a real benefit to be as sure as possible about your dates because then you know that growth scans etc are accurate and your due date is correct. That can make a big difference when it comes to stuff at the end like deciding whether you need to be induced.
All I'm saying is, I know you just want to start trying and it's really exciting, but if you can hold off until you're sure you've had a period, it will probably make dating your eventual pregnancy much easier. Good luck!