@deathandpoetry looks to have answered your question, but I will confirm what he said about how to level cards is accurate. As far as the market goes, if you wanted to make a level 2 beta card you would need 3 total cards combined (the original one plus 2 additional cards). There's no set prices from Steem Monsters but I think you would generally find that the leveled up card is worth as much as how many cards went into leveling it up (in this example 3 of that card) or more depending on what people are willing to pay.