Making Own LED Strip

Well I am looking into making my own LED strip. I am using an Arduino UNO and I know how to setup a strip of 13 LEDS (seeing there are 13 pins I can program on the UNO). But how do I go past the 13 pin mark. How would I make sure they light up in sequence order if I only have 13 pins on the UNO, looking at doing maybe a set of 50 LEDs.

Any help would be great.

What happened to your other 7 pins? You have 20 IO, D0 -D19 (A0-A5 are D14-D19).

Use a MAX7219, wire your LEDs up as if connected in a matrix, but arranged physically in a strip, then send simple SPI commands to the MAX7219 to light them up in order.
$1.25 at

The digits in this unit are driven by a MAX7219, along with pairs of LEDs on the outer bottom boards.
The empty looking sockets at the top middle are actually the breakout from the MAX7219 to the digits.

Use a daisy chain of shift registers to control 1 LED on each output.
This board holds up to 12 shift registers to control 96 LEDS.