Otherwise, put it into your hand. Putting a card into your hand is nice, but you can literally win games by just combining Meren with Spore Frog, which you can sacrifice to prevent all combat damage for a turn - and only costs one mana
You probably won't count on Yawgmoth too much if your only concern is to draw cards, but when looking at the whole package, Yawgmoth, Thran Physician is hard to beat
Where it lands depends on factors such as blues ability to apply pressure, whether there are disruptable mechanics like Heroic or Monstrosity, and the quality of combat tricks and cost of removal
Cephalopod Sentry I want this card to be good
It looks like eBay is the way to go if you need to get rid of commons and uncommons look at how much higher on average you can get for a common/uncommon on eBay versus the other ways of selling