ive come to the conclusion its impossible to actually complete a set of cards
Wait, really? Which ones? I've spent ~90% of my green gems total so far on Hordes cards, and still haven't completed the "Dangerous weapons" card pack, much less any others. You mentioned earlier that you'd done the "Plants in the city", what's the other one? "Miners and equipment"? (Note that I think that cards are cool, not complaining in any way)