If you want to jump in and go, I highly recommend Ruby, though I will warn that Rails can be very imposing if you aren't familiar with web development already.

If you want to jump in and go, I highly recommend Ruby, though I will warn that Rails can be very imposing if you aren't familiar with web development already. If you want to understand more low level concepts, you can never go wrong with C, and these days Rust is a good choice for that as well (though steep learning curve if you have no previous experience).