Get familiar with Linux. They've probably just done programming on Windows machines, but any server work, or data science or scientific programming will involve Linux and if they don't know their way around it they'll be behind.
Startup vs. bigger company. Startup can give you more intense experience, handy when young, but bigger company can give you more stability and reasonable hours, plus if you get in at a "name" company that will look good on your resume in the future.
Web development, the holy trinity HTML/CSS/Javascript. Mention Node, can get you frontend and back end.
Java is in demand at bigger places, will be for short and medium term future.
Mobile development. Developing an app or game by yourself or at a small company won't get you a lot of money, not many people download apps except for the big ones you all use. You can do app development at a bigger company, bank or other places.
Data science/AI. There's going to be a lot of demand for this in the future. I'll mention a few uses, cancer detection, bots. Pay attention to statistics and linear algebra, and near term Python is the language that's used for data science.
Concluding points. It's a career, perhaps more than any other, that requires lifelong learning. After 33 years there's been changes in languages that are used, the tools used, the state of the art seems to pivot every 5 years, and the good ones make the effor to keep up. There's a saying in development about being a developer with 20 years experience vs. one that has one year of experience repeated 20 times.