Which items traded in the columbian exchange do you think were the most valueable why

The columbian exchange was not typically a trade, but more generally  a mix-up of species, including illnesses, such a syphilis!

but the most valuable were perhaps corn and potatoes, as they became very important in the diets of the Old World and many people had more food with their introduction to Europe: they were relatively easy to cultivate and produced a lot of calories.