According to Corey Bowen, a senior game designer at Wizards whos created over 30 precons and also served as lead designer on Spider-Man, the answer is complicated and changes frequently
As long as a card exiled with this creature is a creature card, this creature has the power, toughness, and creature types of the last creature card exiled with it
I dont see any sold copies of this card on eBay (Manabarbs isnt all that good anyways), but listings are posted in the $20-$30 range
If Bruse Tarl and Kraum are your commanders, your deck may contain cards with red, white, and/or blue in their color identity, but not cards with green or black
Giving your opponents cards makes friends, buying time until you can start copying Aminatou's Augury and other wild instants and sorceries to close with