At moment I want to implement picture upload without using any plug-ins.
My upload form looks like this
jQuery ajax does not support file uploads and implementing this manually might be cumbersome. I would suggest you looking at the jQuery form plugin.
Of course you could always check out the source code of the plugin to see how it is implemented if you don't want to include it (it uses a hidden iFrame as files cannot be uploaded with AJAX) but why doing it if you could use it directly :-)
Here's an example how your code might look like:
$(function() {
$('#uploadform').ajaxForm();
});
also make the upload button a submit button: