Here are the determining factors when trying to look fabulous:
1. Calories in vs. calories out: 40%
2. Macronutrient breakdown a.k.a. how many grams of protein, carbs, and fat do I need :
3. Nutrient timing or when do I eat what?: 10%
4. Food quality which would be organic vs. conventionally grown produce, local foods vs. imported etc: 5%
5. Supplements: 5%
Most trainees are overly focused on points 4 and 5, thereby setting themselves up for failure.
To Reiterate: if you do not count your calories you will gain body fat even if you only eat organically grown nuts, that where harvested by happy, unionized farmers and from sustainable trees. The end.

How to set up the caloric needs?
It is really simple: Take your goal body weight in lbs (goal weight) times 8 or 9 (if you are the more sedentary person or a female) 10-11 (if you are in hard training and/or a male)
+ hours of weekly training.

Example: if you want to weigh 200 lbs as a male and train 4 hours a week =
200x (10+4) = 2800 calories a day
Next step: Macro-nutrients
Protein: Comes in at one gram per pound of body weight, in our example, it would be 200 grams at 4 calories a gram = 800 calories.
Carbs: We?ll start with 1.5 grams per lbs body weight, so that would be 300 grams equaling 1200 calories since carbohydrates also come at 4 calories per gram.
800 + 1200 = 2000 calories have been spent. If you are trying to gain weight, you would increase the number of carbs to 2 grams per lbs of body weight.
The remaining calories will come from fat. For that, we?ll simply divide the 800 calories we have left by 9 (since fat clocks in at nine calories per gram), and our hypothetical athlete gets to eat about 90 grams of fat a day?

Yes, setting up your diet will require some basic math and planning and no you do not have to do it. But be aware that your outcome will be sub-par at best if you are not willing to put in the effort. more info here.
Thanks and Good Luck!