You can definitely start now by continuing to education yourself and also practicing some of the tools to help with ADHD. Check out the HowToADHD Youtube channel if you haven’t. Lots of good tools to use as a starting point. Also, reading books and listening to podcasts can be good, as well as forums such as these. If there’s any chance to start working with a therapist right away I’d also advise that too. No need to wait until you see the specialist. Without a formal diagnosis you can still benefit from treatment.