I have found a new way to make filesize as small as you like and still keep the quality high, I thought to share it with anyone who likes to try it:

After finishing go file>save for web> in the new window that opens you'd find a menu to the right in front of the word preset there's an arrow. click on it and choose Optimised to file size.
enter your desired size and put it on Auto Gif/Jpeg. and save it.

I am not sure maybe many here knows about this way. I thought to say it though. :P