Proof of disability card

Hi I have been following this community for a long time while I was waiting to get a diagnosis and now I am newly diagnosed and am wondering if you could please help me with ideas as to what the best proof of disability card would be. I have started the PIP process but have struggled a lot so am now trying to work out what is going to happen next. I have tried to look into different cards but most say that they have PIP as proof to get the card but I don’t have that so don’t know what to do. Thank you