I think a problem with people starting out is that they don't realize that when you become an active person you actually should be allowed more leeway with the types of foods you eat than a couch potatoe. Back in the day people who regularily performed physical labour ate whatever they wanted and looked decent because they had to work so hard.
Now that you are intentionally doing this to gain muscle you can still have what you want, obiously there are some benifites to getting x amount of protein a day and simple carbs after a workout, but those things don't mean shit if you aren't getting enough total energy. Sorry for the rant.
Here's some suggestions that I use:
-cereal, and not just bran flakes
-big ass sub sandwiches, I usually grab a bagette from a bakery slice it in half, grab some lunch meat and presto two huge subs
-MILK lots of it
-bagels are great
-fruit is good
I's a high carb guy so obviously these foods tend to lean toward that macro makeup.
I'm not sure if you are measuring your food intake but that is invaluable if you plan on gaining steadily.