NBA 2K17

3 ways I know to attain a Ruby Player card in MyTEAM.

1.) You can purchase multiple packs of cards & try to get lucky and get a Ruby card, if not you can always sell your MyTEAM cards to gain MyTEAM points & purchase a Ruby card from the auction house. (Depending on how many cards you have to sell might take long, selling the best players for as much as possible would be the best way. Still might take long)

2.) just simply play MyTEAM, all game modes win & collect cards until you reach a total of 650 cards in your collection & you'll receive a reward Ruby Charles Oakley card. (You can also purchase enough cards to reach 650 & get rewarded)

3.) Challenge Tokens, To receive a challenge token you must do the warm up challenge to get started, basically a tutorial on how to complete your challenges. Once completing the first challenge there will be another set of challenges to do, & after that there's another set. I say set because it was 5 games. This might take longer than the other two soloutions because far as of September 29th, 2016. There have only been one weekly challenge, which actually rewards you a Ruby card as well. Cant remember the exact player at the moment but eventually completing all weekly challenges when available will get you a Ruby card as well as achievement.

Easiest way to get a Ruby player in my opinion is to finish the 2017 Thunder collection , they are the only team to give a Ruby ( 88 SF Ricky Pierce ) instead of a sapphire for completing the collection. You can go to collection and press on any team to see the collection reward. You can then simply click the cards you do not have and search for them in the auction house just make sure that you buy the current card & not a specialty card such as moments , droppin 50 , etc... The bronze players were actually what cost me the most out of this collection but it really didn't end up being too time consuming or costly at all.
Good luck !

As of February 2017 (post NBA all star break) packs released 3 new rubies that go for less than 2000 MT a piece. It is definitely the easiest way of getting a ruby as if you don't have 2000 MT all you have to do is quick sell about 4 players.