There is so much crap in processed foods and "snacks" and soda and all that garbage, that I really don't think one has to worry too much about the amount of oil they use to cook their chicken and veggies, especially if it's a healthy oil like olive oil.
Obviously always keep portion size in mind, but as far as I'm concerned cutting out the "junk" is by far more important than trying to shed 100kcal off a meal by skimping on the fats.
Besides, your body needs healthy fats and a fiber & fat -heavy diet is a great way to keep the hunger away if you're trying to lose weight.
As far as snacks go I like apples and cashews, though you've gotta be careful since since it's easy to eat 3000kcal worth of cashews in a day. In moderation though they're actually very healthy. I also like herbal teas when I feel like drinking something other than water. If I'm snacking for genuine nutritional purposes rather than as a treat I usually eat a banana and some yogurt or cottage cheese right out of the carton with maybe some nuts. Chia seeds are good too. If I'm real lazy I'll just chug down raw oats with water, coupled with some protein it'll keep you satiated for hours.
For breakfast I eat bowl of oatmeal and a source of protein and a source of fat every day. That might be yogurt and an avocado or cottage cheese and some nuts. I also drink a glass of whole milk, the kind of raw whole milk that's unhomoginized, untreated, organic, straight out of a cow's tit. For one it tastes fucking amazing, but secondly it has tons of nutrients and healthy fats missing from more processed milks.
Personally I believe in dietary supplements in a "better safe than sorry" type of way. They're not necessary by any means, but I'm not planning my daily diets so carefully as to be certain I could never use more of some micronutrient. If you're lifting, magnesium and zinc are crucial. A multivitamin is nice to have, but keep in mind they are not created equal, and what it says on the package is only half the story. As a rule of thumb the smaller and more "pill-like" it is, the worse it is usually absorbed in the body. Look for capsules whenever possible, they absorb better. Fish oil capsules for Omega 3 or straight up fish oil if you're hardcore. That's about it, unless you take a blood exam and find out you lack iron or whatever.