Generally, there are several options you could pursue.
- Start a stake pool on test-net and then launch one on main-net. How to build a Cardano Stake Pool.
- Get involved with project catalyst. Offer feedback and input to projects that interest you. Try to get involved with a team that has promising ideas. Offer your services where you can fit in. Project Catalyst Ideascale.
- Try building smart contracts using Marlowe. Marlowe Playground.
- Mint your own native token on Cardano. FAQ : Native Tokens (Cardano’s Multi-Asset Support Feature)
- Follow along with the videos for the Plutus Pioneers Program and learn to write smart contracts in Cardano's on chain programming language. Plutus Pioneers Program on YouTube
- Figure out how to mint some NFTs...
- Integration with Atala Prism for identity and certification.
I'm sure there are lots of other possibilities that I haven't heard of or considered. There is no shortage of room to explore for a developer.