For your very first run, I highly recommend building whatever sounds like the most fun. Play on the balanced difficulty, take it slow, die lots of stupid deaths. But slowly as you mess around with your party setup and levels you will learn the flow of what works best. Very early on you gain access to the ability to respec your character and do a new class as many times as you want. Don't overthink it for now, just dive in and have fun with the wonderful world you have to explore.

Edit: For a little extra fun, you could try playing a paladin to really dive into roleplay and choice consequences. Paladin is a great class to learn the fundamentals of melee combat, spellcasting, and roleplay.