nutritional yeast
I add the recommended amount and it gives a shit load of B vitamins + whatever else
Beans.
Beans.
They may be a recurring Lemmy joke but the only reasonable way to get the fiber you need for a day is beans.
Cooked greens, like collards, because they get so small when you cook them, one serving is so full of nutrients and they are one of the best values in terms of nutrition per calorie.
And mostly just eating less junk so more of your calories are nutritious foods.