First off, this is the link for the lesson. Here are some articles that I enjoyed and hope you do too. I'll come up with handout later so check back.
"The Sacred Law of Tithing" by President Gordon B. Hinckley-
"The Lord will open the windows of heaven according to our need, and not according to our greed....It is not so much a matter of money as it is a matter of faith."
"The Divine Law of Tithing" by Bishop (at the time now Elder) Robert D. Hales. "By this principle it shall be known who is for the kingdom of God and who is against it." Also a good point- a part of the celestial law.
From "For the Strength of Youth"- includes attitude is important.
"The Blessings of an Honest Tithe" by President Marion G. Romney- Includes a lot of the same as Elder Hales but also includes Fire Insurance and a good personal experience at the end plus other additional points.
Q&A from the New Era- There isn't much on the topic of Offerings alone by the Apostles and First Presidency so I included this Q&A that has some quotes from President Kimball and talks about how its not so much the amount that matters as much as the willingness to pay that matters.
I hope those give you some good additional insight to your lesson. Happy Teaching!