In order to improve your FPS in Terraria (on a mobile phone), you have to copy the following settings.
Step 1:
You will need to set Parallax to 0%.
And turn on the Frame Skip, and Set the Lighting Mode to Trippy.
And VFX Quality to Low.
Step 2;
You have to turn off Backgrounds, Blood, & Effects.
And turn all graphics to low.
Step 3:
After that, you should be getting more frames.
For PC, you will need to copy the following settings.
Step 4:
You will need to turn on the Frameskip, And set the Lighting to Retro.
You have to turn off the Background, And also turn off Blood & Gore.
After that, disable Heat Distortion & Storm effects, Also, disable the Heat Distortion & Storm Effects.
Your frames should be much better now.