Every time I try to setup an FTP server with user account, I get into troubles. Is there some FTP server with GUI that I can set it up easily? Is there any good and working tutorial for setting up an FTP server?
For GUI options: If you don't need vsftpd, you can use gadmin-proftpd from the repositories.
gadmin-proftpd is a fast and easy to use GTK+ administration tool for the Proftpd standalone server.
If you need something more sophisticated :
Setting up a ftp server should not be a complicated experience though.
I would suggest you try to follow the server guide at https://help.ubuntu.com/11.04/serverguide/C/ftp-server.html and if you get stuck post specific questions.
and administrate it via web interface like : webmin.