Do you think If I did separate the db and the files will make it performs better? and is this easy thing to do? What if I upgrade later on to 2 VPS as well, can I do the same thing without affecting both?
If you are using shared hosting, your database and your site is most likely already on seperate machines and you will not benefit from a second shared account.
If you upgrade your shared hosting to a VPS you probably have to install both the webserver and database server yourself. But you have to benchmark your site to see if you need a bigger VPS or a dedicated server for the database.