For beans, use refried beans and mix with salsa for flavor and keep warm in a crock pot. Or you can make black beans (from dried) and mix with salsa for flavor, cumin, cilantro, etc. Heat in a crock pot.
My favorite (and very easy) chicken taco filling recipe is (makes a nice sized crock-pot full, maybe 8-10 tacos)
4 skinless/boneless chicken breasts
1 jar any type salsa
Put chicken in crockpot. Cover with salsa. Cook on low all day or on high 4-5 hours. Shred chicken with two forks. Add a can of mexi-corn (drained) and a can of black beans (drained and rinsed) and heat thoroughly. Corn and beans are optional but stretch the chicken meat.