The solution for this case is really simple.
After install and configure the vsftpd (https://www.digitalocean.com/community/tutorials/how-to-set-up-vsftpd-on-ubuntu-12-04), follow the steps bellow:
1 - Create an user:
sudo adduser youruser
It will create an folder inside the root /home folder.
2 - Own its folder for root:
sudo chown root:root /home/youruser
3 - Create at least one folder inside its root folder:
sudo mkdir /home/youruser/www
4 - Own the folder to user:
sudo chown -R youruser:youruser /home/youruser/www
5 - Ready! Now you can try to connect via FileZilla or other similar application and transfer files.
Maybe the step 2 is not necessary. Try it. ;)
To me also the same problem.
I cannot connect through FTP, 3 days ago i bought and added droplet on digitalocean. Now still waiting for solution how to connect through FTP. I have posted this on support, but for 2 days there is no response even.
Finally after some hours:
I created users using useradd, and those doesn't work.. i delete it and create again with adduser.. it works!!!
run sudo nano /etc/vsftpd.conf
add the following line
sudo service vsftpd restart