Dual purpose bike

Hello

I am 13 but will turning 14 in the new year in april. For my 14th birthday i will be geting a dual purpose bike. What would be the best bike for me. I would like to be doing a little of both. I would be going to work and back witch is about 15km for when i turn 16 and i would like to be going out to the moutians and do some off roading aswell. I would have to learn how to ride so i would like a started bike but a good bike that i could use in the future.

Thanks
Jamie Hern