First off, you will want to get optifine. If you are generally not that good at installing mods, i suggest getting magic launcher as it is a really handy and simple tool for getting your mine craft mods. Once you have optifine installed, change your render distance to the lowest setting, and maximize the fps option. You will also want to toggle off rain and snow.

If you are really struggling at a low fps, I suggest getting a 4 x 4 resource pack, it helps a little.

Run a security scan, or clear out files from your computer.

Devote more ram into minecraft.

Remove any programs from your computer that you do not use.

Close all other browsers/tabs while running your minecraft client.

Change your fancy graphics too fast. Turn off fog. Minimize your render distance. Select Max FPS. Smooth lighting off. Clouds off.

If you are unaware how to check your fps, click f3 and it will pop up on the top of the screen. Or go to snooper settings and it should be relatively at the top.