I have an Indian buffalo head coin from 1936....what is its value?

These are very common. In good condition, it is worth roughly $2-5. In excellent condition, it could bring as much as $50-100. You may have seen some online that are proofs selling for $5,000+.

I have been told that you can be among. $ 3,000 to $ 20,000

It depends if you have errors, such as only THREE legs in sight for the buffalo. But usually like $ 10.