Hello there! I'm using a 7" TFT LCD as well, I opened the config.txt file from boot and did some changes to make it work with my screen, and it works great! These are changes I made in the /boot/config.txt:
First,
Uncomment "disable_overscan=1"
Then, change the following values
overscan_left=24
overscan_right=24
Overscan_top=10
Overscan_bottom=24
Framebuffer_width=480
Framebuffer_height=320
Sdtv_mode=2
Sdtv_aspect=2
And, make sure to save while you exit the file.