Python and JavaScript - both are quite easy to learn and good for starting. Python is more universal I would say, but if you want to focus on apps, frontend, them JavaScript is your preferred choice.

SQL - is a must, but how much is needed will depend on your role.

Rust - is getting more popularity out there, especially in the Bitcoin space. Check it out if you will be focusing on the backend more.

There is a nice material by Braiins - https://store.braiins.com/products/building-bitcoin-in-rust