Board Thread:Card Unit Builds/@comment-110.55.4.76-20150219035000/@comment-25435121-20150305201050

You should evolve first if possible. Arcana bonuses are added to the base stats unlike friendship which is added to the blue portion. i.e on your card you'll see something like this:

Attack: 6000 (+132)

The 6000 would be the base stat of your card (at it's current level/evolution), the blue part in parenthesis are bonuses applied from various sources which include Buildings, Friendship, Items, and Unit Bonuses.

The arcana upgrades the base stat (6000 in my example above). If you read up on Evolution & Amalgamation you'll see that the stats are not always carried over. At most for evolution you will retain 15% of the arcana you spend on it. For amalgamation, you will keep at most 8%.