Start planning....keep in mind your family schedule...you don't want to plan a meal that takes long to cook when you have activities planned that get you home later than normal....those are the nights for simple meals - soups and sandwiches, a roast that's been cooking all day in a slow cooker, something along those lines (and yes, sometimes our family does chicken nuggets and french fries because they are fast and easy, the kids will eat them, and it gets everybody back on schedule when we have late nights).
If you do a roast and have a good amount leftover, it does NOT have to stay as a roast. You can add the leftovers to a vegetable broth with fresh veggies and have a yummy soup; throw shredded roast in with cooked (and cooled) rice, some soy sauce, veggies and you have a beef stir fry; slap some on some bread, add cheese and heat, and you have a quick and delicious sandwich....there really are LOTS of recipes you can use to turn leftovers into completely different meals. The trick is to go through your cookbooks (or find recipes online or check out some books from the library) and have some ready to go.
Remember to have variety...while you might like red meat several nights a week, most people's bodies can't properly digest a huge amount....alternate with poultry (ground turkey instead of ground beef in spaghetti makes a healthier meal with little to no taste difference), seafood, or even meatless meals (3-cheese tortellini in marinara sauce, for example), and change up the vegetables as well....don't always have broccoli or some other vegetable as you and your family will get sick of it...alternate....have fresh salads every few nights, introduce new veggies every now and then (a big one in our house is the California blends either plain or with cheese - these are broccoli, cauliflower, and carrots..nice and healthy).
Those are the basics.....as you get more confident, you can add salvage stores to your shopping routine - GREAT discounts on the supplemental foods - side dishes, condiments, drinks - but seldom on meats.....now, take a deep breath and get started!.....Next up...basics of saving on the things kids need....