What do i need to upload from my gwt project to web hosting? its just html or all project files?
You'll only need to upload the html files, the css files, and your java file. Also, any other file linked to within your html files need to go in the same directory.
Any modern Java IDE gives you an option to export a web project as a war module. If your are not using an IDE, it depends:
If you just write your code under client folder, no need to upload any .class files to the server. You don't need any Java Application server as well, and a normal HTTP server (such as Apache) would suffice. An example of such a GWT application is GWT showcase which is included in GWT download package.
If you have any server-side code under server package, then you should upload .class files (under WEB-INF/classes folder in your web modile) as well as the rest of .js, .css, .jpg/gif, .html files. In this case you need a servlet container such as Tomcat to serve your server-side code.