To become a Blockchain Developer, you need to understand first about the blockchain and the technology behind it. Once the basics are thorough, read whitepapers and resources that will help you better about which platform in the blockchain technology best suits you. Once that is covered, you can master a few programming languages to help you bag better job opportunities like C++, Java, Python, Solidity for Ethereum, etc.
You must also learn more about Cryptonomics, Cryptography to help you become a qualified Blockchain Developer. To become one, I recommend you check out the Blockchain Developer Course. Also, watch the below video to get a better insight into how learners react to this course.