High carb and protein foods are best when going for mass. Pasta, potatoes, yams, fruits etc are best on the carb arena. Meats, eggs and MRPs are best protein sources. You need to remember to eat several times a day, keep the nutrition pumping in throughtout the day (but keep to your target caloric intake, just divide it into 5 or 6 meals).
Heavy and slow will pack the muscle on. While it isn't exactly _necessary_ to be sore in order to be doing good, I feel stagnant when I'm not sore at least a little. The soreness is damage done to the muscle while working out and mass increases from repairs to the damage. Logical enough, yah?
And drink lots of water. I can't stress the importance enough. It keeps kidneys in good working order, flushes out the system and hydrates body/muscles throughout the day.
I wouldn't worry about supplements from the start. When you get "serious", muscle will come easily in the beginning. Don't waste money on them at that point. If you plateau later, maybe look into it.
tips on building muscle... 
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