To be honest, it looks moderate. I don't mean to scare you but ich can be a tough bugger to get rid of. In a .5 gallon, waterchanges should be done every other day. Ich is caused mainly by stress and poor water quality.
What you want to do is do a water change and add some aquarium salt - not table salt! - to your bowl, get an adjustable heater and keep the range within. You might also want to use a different container, such as a Rubbermaid storage bin, for a hospital tank. This way, you can treat your betta without much risk of infecting his original home. The temperature of the water should be no higher than 82 degrees and no lower than 72 degrees - slowly raise the temperature to 82 degrees since ich thrives in lower temperatures. Go to the petstore and look for a medication called Coppersafe or Malachite Green. Make sure to treat him for up to 14 days even if he looks like he's doing better.
Here is a very good link to a better explanation of Ich and what it is:
I hope he gets better soon. I'm sure he will with proper meds and things ... sorry he's ill. Any other questions feel free to ask the forum :)