reducing size of an image in gimp

[Abhishek Dixit]

based on a suggestion I am using the following packages for Nautilus:

nautilus-image-converter - nautilus extension to mass resize or rotate images
nautilus-image-manipulator - Resize and send images from Nautilus

I have a context menu by right-clicking the images where I  can rotate
and resize the images in the simplest way.
The size of image I have been able to bring in permissible range 20-50
kb but the pixels of image are also limited to be not more than
200x230 kb if I reduce the pixels then the size becomes less than 20
kb is there a solution in this situation?
Basically I have to keep the pixel size and byte size limited that is
the situation is hit and trial the only way to go?

the image is in jpeg, I am on Ubuntu 12.04 64 bit,