You need sources of fat, cholesterol, and protein to maintain performance nearer to optimum levels (be it physically, emotionally, or mentally). Make sure you are getting enough first, then start counting calories after that. If you need to cut things out, start with simpler carbohydrates first. Meat from animals raised on hay or silage (also known as 'grass fed') have radically different lipid and micronutrient profiles compared to grain-fed animals. Egg yolks are a great source of essential cholesterol, and also have many hard to accumulate micros besides (as you might expect from something meant to solely fulfill the nutritional needs of a developing organism growing it's CNS). Butter is a great way to add calories to a meal without spiking your insulin (in point in fact, insulin is even more anabolic than testosterone, which is why bodybuilders frequently dope with it alongside HGH), and it also provides some cholesterol as well. Everything that applies to meat in terms of effect on product applies just as much as well.
You need green leafy vegetables, and cruciform vegetables in particular, to get your extra large theraputic doses of most micronutrients. You can just eat lots of them without greatly affecting your calorie intake thereby anyways. Some people don't eat lots of green leafy vegetables, and hence have to try to make up deficiencies in their micros by buying multivitamins. This is foolishness of course. That being said, there are some micronutrients that can never the less realize increases in benefit even with very large doses through supplementation, such as vitamin c, or are otherwise difficult to source in diet all on their own to levels of greater benefit, such as iodine or vitamin d. (As a general rule, 'daily recommended' values are realistically 'bare minimum for continued function' values.)
Not all carbohydrate sources are created equal; even if you are bulking, it would be well to avoid materials that are high in lectins, such as most grains or legumes. Likewise, even if cutting, it can still be good to have a small bit of carbohydrates, and things like sweet potatoes, green peas, or chickpeas are good sources low in the sort of anti-nutrients that can make other plants in their class problematic. (A procedural exception would be the process of nixtamalization, or limewashing grains, where the alkali chemically neutralizes most of the lectins in the bran. Perhaps not so relevant too you at the moment though since you will likely be cutting carbs anyways. Something to keep in mind for bulking though, when looking to gain mass increases in insulin are a bonus.)
Im ambivalent about dairy; anecdotally, drinking milk neat gives me brainfog. I personally prefer to use it only if it's 'pre-digested' in some way, like fermentation (ie cheeses, sour creams, cultured buttermilks, and et cetera), or thermolysis (also known as, cooking with heat), or physically separated from most of the portions that can carry potentially problematic parts in some way (like butter). (As an aside, not all forms of fermentation are created equal; i personally avoid things fermented with yeast, which has been known to cause issues with some people.)
Water soluble fiber is the kind most relevant to gut health; microbes metabolize it and produce short-chain fatty acids as a by product, which are the primary energy source for your intestinal cells. Incidentally, it also slows down absorption of sugars in the small intestine, which evens out potentially damaging insulin spikes. Things like green leafy vegetables, avocados, sweet potatoes, peas, or lima beans, have lots of soluble fiber. Many fruits have some soluble fiber, but you may not want the extra sugar that comes with them (i personally make an exception for blueberries though). Citrus like grapefruits also have soluble fiber, but citrus juices like orange without pulp is basically a pure sugar spike with all the benefit removed.
A few words on fats: they're complicated. A few more words: generally, fats from animal sources or fruit sources (like olive, coconut, or avocado) are most amenable to processing by the human animal, while fats from grains or seeds (like soy, canola, or safflower) can cause problems. Fats from tree nuts occupy something of a middle ground, not especially great, but not particularly bad either (hazelnuts and macadamia nuts are amongst the best though, and if you like almonds or cashews those are fine too). Mytheo-poetically, you could see it as a difference between things that want to be eaten (fruits), and things that would rather not be eaten, if you please (grains).
On a more technical level, the lipids you want to avoid are ones with high volatility, also known as 'drying oils', that readily undergo autoxidation, producing free radicals. A graphic demonstration of this fact can be seen in how if, for example, someone makes the mistake of leaving a a pile of linseed soaked rags in a bucket somewhere, the heat produced exothemically by their oxidation can cause the whole thing to spontaneously combust. This is roughly analogous to what happens when it's inside the body.
The most stable oils are saturated and monounsaturated fats, while polyunsaturated fats are the most volatile (and hence should generally be avoided in cooking or consumption). This is a basic rule of thumb. A fact that complicates this rule of thumb (or perhaps rather 'adds nuance', if you will) is the fact that the much touted omega-3 oils just so happen to technically be polyunsaturates as well. You can refer this back to the 'animal source' rule of thumb with respect to fish oils. Amongst the three, docosahexaenoic acid (22 carbon 6 double bond) is the most important. Eicosapentaenoic acid (20 carbon 5 double bond) is useful in the sense that the body can more easily convert it to DHA. Alpha-linolenic acid (18 carbon 3 double bond) is the last omega-3 and takes the most difficult pathway to DHA conversion. There are some plant sources of ALA, like walnuts, but however much ALA they have is so often frequently coterminous with a significantly greater amount of other volatile polyunsaturates as well, so as to make a hash of it (one notable exception however would be chia seeds). (Ps, never heat an oil past it's smoke point [or char your meat or any other food for that matter], as this produces carcinogens).
As a general rule, you basically want to avoid consuming substances that your body does not have metabolic 'pathways' for, especially if they can be absorbed into the bloodstream anyways (like heavy metals or plasticizers). For a topical example things like artificial sugars, or things preserved with microtoxins like BHT, TBHQ, benzoate salts, nitrate salts, or propionate salts, or things like petroleum based food colouring (often denotated as [color] #[number] on ingredient lists). A bit of nuance to further illustrate the dynamic by example would be ethanol, which is by degrees toxic to humans, but they also have a pathway to metabolize it as well, so occasional consumption would not incur lingering knock-on effects of persistence.
And, make sure to get 8 hours of sleep and 2-4 quarts of water a day.
