Just play in the Arena and get a win streak to get to the special spins at the end.
^ That. Course if you've been away so long you don't know what shards are, then the arena is probably new to you as well.
The arena replaced the Top50. There are 4 leagues divided by difficulty and level. Decks are made/submitted by players, who receive a certain amount of "skill points" based on their level, which is dependant on score. Points are spent on upgrades to health, # of upgrades, double draw, and mark multiplier. Basically, if you're level 80, your arena deck is of false god power.
Now, winning a set number of games in a row gives you a special spin. The special spin is filled with rare cards. If you don't win a rare after the wheels are done spinning, you get to respin any individual column that you wish, up to 3 times each, until you do get one.
Bronze League = Level 0-19, 5 wins in a row, unupgraded rare card spin
Silver League = Level 20-39, 4 wins in a row, unupgraded rare card spin
Gold League = Level 40-59, 3 wins in a row, upgraded rare card spin
Platinum League = 60-80, 2 wins in a row, upgraded rare card spin
It's also worth mentioning that if you can build a deck capable of reliably grinding at least silver league, the arena will be infinitely more profitable then grinding AI0-4. Happy hunting.
