Joanna is a disciple of Jesus with minimal reference in scripture. Her story is found in Luke 8:1-3. While information is not abundant, you can find enough to establish a theme and tell her story for your pillar project if you choose her.
A good place to start is Women in the Bible.
Bible Gateway offers information.
A character study on Joanna.
An Orthodox Church view of Joanna.
More information on Joanna.
An informative study on Joanna and her life. Lots of good information here.
An interesting piece on how God worked through Joanna to fund Jesus’ ministry with Herod’s money!