Here is a link for how to evo cards.
http://rageofbahamutguide.blogspot.com/p/evolution.htmlSome suggestions and info:
When evolving HR and up cards dont do below a 4-7
When evolving SR and up cards a 4-7/5-9 is usually recommended. Anything above that is usually not worth it.
Most popular evos are 4-7, 5-9, 6-11
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The first number is the cards used. The second number is the amount of cards maxed. So a 4-7 you start with 4 cards and max 7.
Here is the diagram for a 4-7
