MissB!
Positions in nutrition change all of the time with fad diets, new studies etc so I like to stick to the basics. I don't buy into the newest crazes etc but I do research everything before I put it into my body really.
I'm a hick from northern Idaho and was raised in hunting and farm country. What city folk call "organic" we call "sh!t out of the garden". I guess I look at it like this, mother nature knows best so I keep things simple for myself as much as I can and steer away from most of the processed foods out there as they are packed with saturated fats (bad) and sugar, which in our society is used excessively.
Sugar (and high fructose corn syrup etc) does a number of things to the body when taken in excess, nerve damage, blood vessel damage, heart damage, kidney failure among other things. I'm sure Cheryl will be along shortly and express her view that sugar causes inflammation which increases the risk of cancer (she'll also probably have a few "autocorrect" issues as she'll be using her iPad lol). I haven't read up on the science of that position so I won't comment on it, just that we understand that sugar is a culprit to poor health, weight gain and other chronic conditions like diabetes.
Starches like potatoes and white rice will raise blood sugar levels in the body as well due to how the body processes them, processed white flours will do the same. The more we can control our glycemic index the easier it is to maintain a healthy weight.
Stay away from saturated fats for the most part, but keep in mind that not all fats are bad and our diets should consist of between 20-30% of good fats, mono and poly unsaturated fats like Olive Oil (although at temperatures over 320 degrees this becomes hydrogenated which makes it bad for you) Canola Oil (good for cooking over 320) coconut oil & butter (medium chain triglycerides) nuts, fish etc. Focus on good Omega 3's and controlled Omega 6's (in a 1/6 ratio).
Focus on fresh fruits and vegetables or frozen if not in season, lean meats (depending on your dietary views of course like vegan/vegetarian) like lean beef, lean pork fish, and turkey, white chicken breast etc. I like to know where my food comes from so I buy locally produced fruits and vegies (and grow some) as well as locally raised meats which is easy for me due to where I live (BFE Idaho). But really whatever you have access to.
Eating healthy doesn't have to be a daunting task, I'm on almost an exclusive liquid diet due to after effects of treatment and surgery so I blend, juice and use protein powders etc.
Healthy ratio's in gaining weight you should really focus on lean proteins and good fats while controlling your carbohydrates (complex carbs, whole grains etc) to around 40% of your diet.
Hope that helps, and just to be clear I'm not a nutritionist, just a hick from Idaho

Eric