Join an eth global hackathon and find a team to jam with.

http://ethglobal.co/

Play with solidity, deploy toys to test nets, tuna local node.

https://solidity-by-example.org/

https://eth-brownie.readthedocs.io/en/stable/

That’s if you are interested in contract/transaction layers. If you are more interested in the main chain then look into go-ethereum or erigon clients.

Cadcad is also a popular for playing with systems design/modelling for crypto projects https://cadcad.org/