I was wondering if it was worth spending like $50 for packs because I am still fairly new and the only good deck I have atm is a mech aggro mage.
or is it worth buying naxx or blackrock

Buy expansions and a 40 pack

Naxx and Blackrock have really good cards.
I'd say figure out what deck you really wanna play, and invest accordingly.

I enjoy playing mage and priest and I think Naxx has some good cards for both

If I could get all my cash back that I ever spent and quit the game, I probably would.

But in reality, I'm invested, so I'll spend a buck here and there to keep up with the expansions.

My answer: Spend $60 if you're willing to spend more later.

expansions are nice ye

Both expansions are more than worth it and a 40 pack will most likely enable you to craft a legendary in addition to the ones you may pull via rng.

If you are truly strapped for cash and cannot afford both then I would go with the expansions.

I won't spend any money right now, maybe in the future.

Better than spending it on hookers I guess.

Debatable.