You will need a gradient and/or shadow on each of your 3 Minimal posters. Try to keep both textures and gradients subtle.
Complete the Gradient Practice document found in the folder: Shared > Students > Fine Art > Lessons 6-10 > 08 Gradients. First watch the Gradient Tutorial below.
Make sure to watch the Texture tutorial on Opacity Masks. I have saved textures you can use in the folder: Shared > Students > Fine Art > Lessons 6-10 > Textures. Select a texture you like and Ctrl + C to copy and Ctrl + V to paste on your Minimal Poster.