Where are you finding these $10 uC at my I have bunch I'd sell back for that price LOL
http://www.taydaelectronics.com/ic-integrated-circuits/microcontrollers.html
Atmega 328 $3.50 each
Banggood.com $2.00 each
Ebay less then $2.00 each
leds 2 cent's resistors 1 cent
disbelief going to cost you your time and money.

And I would go with a 28 pin chip most have 18 to 20 I/O pins open.
and coding would be dead simple. I showed my 9 year old twins 6 years ago how to light the M of their first name
with a pic18f2550 it took them maybe a hour to have them leds rolling around the way they wanted it to.
They even soldered it. no pwm but I'm sure they could've figured how it works too.
You don't need PMW you make a array holding the led you want lit.
then you send the lit leds out in a loop and start sending blanks with them off loop it right and you have fading and blinking and what
ever you want to happen just like film of a movie.

i did a search in the whole Atmega database and got this: ATMEGA1280
see the price on their website.....

anyway. ive got some solid idea, i will just use ATmega328P for it. Thanks everyone! ive got an idea of doing some sort of a multiplexed system that would do what i need perfectly. Just got hit by a memo stating that my exams are starting in a couple of weeks so ill be seldom on. will post the details of the finished products when it is finished

 

This is 8 leds on 4 pins you can add 16 on 8 pins or just use 15 or 16 pin per pin.
Each led lit is like a frame you just change frames loaded from a array if you add blank frames to keep leds off more
in space and time it would fade the trick is not to see lit flicker but what the heck old movies flickered and we still watched them
if you're old enough to remember that. I used the arduino to program the atmega 328.
Like Mike said the table data takes time to write because there big arrays of frames but it works this is just rolling leds took about 10 minutes
to write.

You can put 20 on 5 pins and use a smaller chip that your arduino can program it can be used to program as a ISP programmer.
The downside to 20 leds on 5 pins is a mistake in frames is harder to find because of how you light the leds by sinking and sourcing power takes more time to debug a backward led and a mistake could take the better part of a day to find