I'm completely new to this card game and I want to buy it, but after I buy the core set, what should I get? There's tons of expansions, and I was just wondering if you guys could help me. Thanks!

It depends. If you have someone you are playing against who has their own stuff, I'd recommend picking your favorite house deluxe expansion first and slowly pick up the others. You will probably want to get another core set, but that can wait till later. Check the sticky, it has some really good links. Happy gaming.

What do you mean "the sticky"? I don't know anyone that plays it, and I think I want to play as a House with a lot of military power.

The thread that says "New Players Welcome!" at the top of the forum. There's a link in there to another thread that has a lot of useful information about Houses, what to get next, deck building ( as you say you wanted something very strong militarily) etc.