Welcome to the forum.
Large displays typically use LEDs in strings for each segment. Common is 3,6 or 9 LEDs. Each set of 3 has its own current limit resistor and is powered from 12V.
6 makes a nice tall digit.
You need a buffer/driver that can handle the current and 12V. TPIC6B595 is great for that - 150mA current sink capability from up to 50V source. Each one can control 8 segments. Use 2 for a 14-segment display.
I have several boards that combine Arduino functionality and 3,4, up to 12 TPIC6B595s, here is the largest one; an offboard FTDI Basic is plugged into the corner for programming.
http://www.crossroadsfencing.com/BobuinoRev17/
