MArcomage

Is the price for playing the card first deducted and the attack delivered with the remaining ressources or are the ressources counted first and afterwards the price deducted?

Unless it somehow bypasses the standard rules, the cost is always deducted before any internal card code executes.

You have to play the card first in order to "activate the effect stated in the text description.

So it will first deduct your resources. Then convert the rest resources into attack.

However, cards that have an additional effect that reduces your resources see that effect occur at the very end of your turn. If you have only 17 gems and play Vampire, it will consume the gems for its cost, deliver the attack, reduce your Magic by one, grant your production (based on the new Magic value), and THEN subtract seven additional gems. Unless your Magic is greater than seven after the reduction, you would then have zero gems.

This is notably different from the 3DO Arcomage game where production occurred at the beginning of each turn rather than the end. If Vampire existed as such in that game, the -7 gems tagline would have had no effect in such a situation.

Cost is always substracted before the effect, so "All alemental attack" turns the remaining resources into attack.