Thats what i love to hear man, someone who understands a good ammount of the
40k background before they come into the game

makes gamers who arnt just going to make epic cheese armys only to win, but people who make fun armies based off of the fiction, but dont let me delude you, still need to have a competitive edge otherwise you will just lose and you will grow bored. also may i say that every newbie and his dog goes space marines first, and space marines suck man haha
id go either guard or necrons, they are probably the best armies in
40k and they are both full of background and you can have really fun army lists man