Well, seeing as a lot of people want some type of trading.. I suggest an auction house
AH's are used in a large variety of games ranging from World of Warcraft to on of those mediocre text based RPGs(duels, gladiatus)
In most cases auction houses come with a Min-Bid/Buy-Out option. For Elements however, I suggest we take out the buy out option(as this will cause abuse) and stick with only a Min-Bid option.
With only the Min-Bid there can also be abuse, so I suggest that there will be 4 time limit options. 1 hour, 3 hours, 8 hours and 24 hours.
With the auction house we can have trading without fear of getting scammed or abuse, and would add more fun to the game.