Don't worry about the red clay... they don't need it... although it is good for them.
My pigeons have never had the red clay in 10 years and they are all very healthy.
She has eyes like an owl... stunning.
Well done for rescuing it.
As for feed you have good advise already... just to add a standard wild bird mix is great for small numbers of pet pigeons... you can add chicken layer pellets to it for extra calcium and protein... and you should have a bowl...