Getting enough fiber day to day usually comes down to a short list of foods eaten regularly, rather than one big effort. A few worth building meals around:
Oatmeal
A quarter cup of dry oats gives about 5 grams of fiber, most of it the soluble type called beta-glucan, which is part of why oatmeal keeps you full longer than a bowl of cereal does. Stick to plain oats rather than the flavoured sachets — those carry a lot of added sugar for not much extra fiber — and sweeten with honey or a chopped date instead.
Lentils
A cup of cooked lentils runs about 15 grams of fiber and 12 grams of protein, with almost no fat, which is part of why they're a staple across South Asian and Middle Eastern cooking. Lentil soup with brown rice is an easy way to get both fiber sources in the same bowl.
Raspberries
A cup of raspberries gives roughly the same fiber as three slices of whole wheat bread. This sweet fruit works well stirred into breakfast cereal or eaten on its own when a sugar craving hits.
Dates
A single Mazafati date carries close to 1.5 grams of fiber and, unlike raspberries, keeps for months without refrigeration, which makes it an easy one to always have on hand.
Getting there without overdoing it
Adding a lot of fiber at once tends to cause bloating, so build up over a week or two and drink more water as you do. Splitting servings across the day — oats at breakfast, lentils at lunch, dates or raspberries as a snack — works better than trying to hit the daily target in one meal.