if you want to trade for a card, use the trading area in the forums. head over there, read the rules, create your trading thread and scan the others.
for a 4* team... really any 5 you have maxed will do.
for a lower tier team the skill priority is:
Pois > KB > Slow > AA
you only want 1, 2 max poisons and just because AA is at the bottom doesnt mean its not really usefull. Also speed matters but really if your taking a team of 4*'s make sure they are maxed.