Please follow this video tutorial and you will see a small thing can reduce the file size easily. It was really helpfull for me.
How to Reduce AI Vector file size: An Adobe illustrator Tutorial
My AI file size was not going under 1 MB even by deleting extras so what I did is I opened a raster small image of 100 kb with Adobe Illustrator. then deleted the image and saved the file as AI. Then I Copied the whole vector content of original AI file that was bigger then 1 MB with ctrl+c command and pasted it in the new file created with raster image. and saved it. Wow the new file size is only 137 kb now.