About the capture cards, you're correct that you can only capture certain creature types with the type of the card, however gold and diamond allow you to capture any type.
There's no alpha card for other types such as normal/ice/flying/etc, only gold and diamond will work for them. However there'll be different card designs u can craft for other types.
This places even more importance on the gold and diamond cards and is a reason we increased the odd chance for gold and diamond in the end as to allow more creature types to be captured with them.