@mike: I'll be honest with you: right now, everyone is basically running control shells with C'Thun and his disciple cards in Standard. I would take advantage of that HEAVILY right now. You could also look into just crafting one particular deck that is cheap on dust, then stomping out matches with that on a regular basis to get gold to get more packs.

Also, the Adventure packs are worth it. Almost every legendary out of them is meta, and even the commons and rares out of it are meta. Those are complete value to spend money or gold on, either way.

I went the easier route for getting into Hearthstone: I bought the Adventure packs and then bought 60 packs of classic. From there, I dusted what I didn't need (and got lucky that I could dust Naxx stuff) and made a Combo Druid deck. Therefore, it's going to be a bit difficult for me to actually suggest a solid way to get in, especially since you can't buy Naxx anymore and dust those cards for a shitload of dust.

I would also suggest checking out two guides online:

• Comprehensive (safe) disenchant list for new players: There are tons upon tons of cards that will literally never be viable in a competitive setting, much the same way as most commons and such in MTG. This is a little old (July of 2015), but it's still a legit list. This will help you thin your collection down to the Grade A prime cut stuff and get you dust for all that trifling bullshit.
• Arena Tier Lists: If you plan on going the route of playing a lot of Arena, the Icy Veins Arena Tier List is a mandatory read. They break down what the best cards for each class is in Arena and help you to build a stronger and more viable competitive deck that hits mana curve well while also giving you the most bang for your buck.

Last but not least, Classic packs have a higher chance for Legendary cards to get packed, so I would focus on those if you are looking to build up your collection as well. Just dust the shit cards and craft the good stuff.

Good luck to you on your adventures, Mike.