Here you will find some useful resources for Gospel Lesson templates for each different division in TNTT / different age groups. I have personally tried these templates in the past throughout the few years that I have taught the youth from different age groups (elementary to high school students), and I think that these templates work pretty well.
Again, simply use this as a guide and modify to fit your needs.
A reliable source to obtain the readings of the day / week are from the USCCB (United States Conference of Catholic Bishops).
When preparing for a gospel lesson, getting the gospel reading for that particular week (Sunday) should be your first step.
NOTE – To change the date of the reading (other than today), edit the date in the URL.
To assist with researching about the meaning of the gospel, a great resource to refer to is the Catechism of the Catholic Church. See below
The easiest way I found to begin researching and preparing my lesson plan is to look at the general layout of the TNTT (VEYM) Weekly Gospel Lesson for a particular week. The weekly gospel lessons give you a general sense of what the gospel is about, but as a teacher delivering the material to the youth, I believe that the individual needs to take it a step further to do more research so that your understanding of the material is “solid”. See below for a useful resource from the VEYM on weekly gospel lessons. Choose the gospel lesson from whichever age group suits your needs.