All good advice on here. Food wise, stick to an anti-inflammatory diet. Eat plenty of greens and stick with chicken, turkey, and fish for animal sources. Nuts can be expensive depending on what kind you get, but they're packed with energy and fiber when you need something simple on-the-go. Finally, I highly recommend eating plenty of yogurt. There's this stuff you can find at any major grocery store called Kefir which is considered a "cousin" of yogurt but it's basically the same thing. There's different flavors if you're picky, and it has a lot of probiotics in it which help the immune system, but also helps you poop excellence.
If you don't eat a lot of fish, taking fish oil capsules will help a lot with the inflammation, along with the balanced diet. Also, taking megadoses of vitamin C are good for preventing you from getting sick. Taking a gram or two a day is completely safe and a lot of people, including myself have done it. I never get sick and I attribute it to steady water intake, probiotics, and the vitamin C.