How do I set up a diamond trade? Meaning me giving something for diamonds, but to a specific player or something.

To my knowledge, I think that you cannot trade specifically to another user for diamonds. However, you can notify the user right after you set up the trade and hopefully they will be the first to purchase it.

To set up a trade, heres an example.
Say I want to trade a pair of butterfly wings to you for 500 diamonds.
1) First I send the butterfly wings to you for free and you will see it in your 'Trades'.
2) I will then set up an exchange of 1g for 500 diamonds in the 'Exchange'.
3) You will see the exchange by choosing the 'Gold' option in the drop down menu of the search exchange button.
4) Accept the trade, and vola! Business done :3

Steps 1 & 2 can be done in opposite orders

Hope this helps!! :3

Thank you!