Sorry for the delayed answer. I had a problem with the site. I was unable to write anything on the forum. I know that some users had the same problem. But now it's ok.
So basically, for the dialog system, I used an array. First I filled the array at the beginning of the layout with all the dialogs of each character. I used a 2 dimensions array by the way. That way, I knew exactly where was the dialog of each character.
I used the first index as an ID for the character and the second index as the value of the text. For example, the gardener's ID will be 0 and all these combination will be for the gardener [0,0], [0,1], [0,2], etc. Let's take an example. In the Array, the value of [0,0] will be: x=0 and y="Do you want to help me clean my garden?".
Then, to rotate the dialog, you can use a simple loop and make sure that everytime you reach the end of the serie of dialog for a character, you put the iterator of the loop at the beginning. That's how you make the dialog loops endlessly.
I hope this will help you. I will try to make a simple capx file for this for you to better understand. I don't have a lot free time because I'm working but let me know if you have other questions.