To contribute to the blockchain is you can run your own node. If you wanted to donate then I suggest you donated to the developers who are trying to make bitcoin better. Holding your own bitcoin in my opinion should also be contributing to the blockchain since you are making a transaction and it should be recorded in the blockchain when it is confirmed. Using it in your business is also helpful for bitcoin since it is what satoshi made it for.
To support the Bitcoin blockchain, operating your own node is a proactive step that strengthens the network's infrastructure. Another impactful alternative is donating to the core developers dedicated to perfecting Bitcoin, driving innovation and maintenance. However, contributing doesn't stop there. Holding your own Bitcoin also represents support, as every transaction you make validates and expands the blockchain record. Furthermore, using Bitcoin in your business context aligns with Satoshi's goals, facilitating its use as a functional currency. All of these actions collectively increase Bitcoin's decentralization, security, and practical adoption, solidifying its position as a sustainable monetary system.