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