For basic appliances with an very specific task, an complete Raspbian Installation can be too heavy weight and unnecessary. Striping down Raspbian of things like Mathematica can be time consuming. Enter Minibian: Just download the Image at https://minibianpi.wordpress.com/ and flash it to your SD Card like a normal Raspbian Image. Following is the procedure to setup Minibian with raspi-config, rpi-update and sudo / Default User pi.

How much resources does Minibian need after installation?
About 469 MB of space on the SD Card.
About 60 MB of RAM.
I think that is way better than Raspbian.

apt-get update  
apt-get install -y raspi-config  
raspi-config
# Default Configuration and Expand Filesystem using raspi-config  
# Enter Finish and press Yes on Reboot the Device

apt-get install -y rpi-update sudo  
apt-get -y upgrade  
reboot

rpi-update

Create Default User pi

adduser pi  
# Enter Password as wanted, i.e. raspberry  

Add user to default groups

usermod -a -G pi,adm,dialout,cdrom,audio,video,plugdev,games,users pi  

Add sbin Paths to pi

echo 'export PATH="$PATH:/sbin:/usr/sbin:usr/local/sbin"' >> /home/pi/.bashrc  

Add user to sudo

visudo  
# Add under  
# # User privilege specification  
# root ALL=(ALL:ALL) ALL  
pi ALL=(ALL:ALL) ALL  

Save and Exit

reboot

Disable root login

sudo passwd -l root