Tomatoes are particularly good at preventing prostate cancer. Greens have also been found very beneficial. Whole grain wheat and rye have been the best studied, but rolled oats, and brown rice have a few studies. Many studies have found refined grains, including white rice, to be harmful. Low salt nuts are readily available at no extra cost.
Peanut oil is very good, too.
Avoidance of partially hydrogenated oils found in many processed foods, and avoidance of butter are both wise. Soy protein has also had a lot of favorable news recently. Beans and peas are inexpensive, especially when bought in dry form. The cheapest way to buy soy protein, other than soybeans themselves, is TVP or soy flour. Powdered soy milk is also inexpensive and available.