This is a staple in our house
1 4-5 pound roast (any kind will do)
1 can french onion soup
1 package dry ranch dressing
approximately 4 cups of water (depending on size of your crock pot and roast)
So I add enough water to cover about half of the roast. I mix the dry dressing with 1 cup of hot water and pour over roast. No need to stir, it will mix up on its own. Then pour the can of french onion soup on top of the roast, slowly so the onions sit on top (see photo). I cook on high for 6 hours and then usually turn to low or keep warm depending on how done the meat is after 6 hours. It will literally pull apart and you'll have a nice onion gravy. We will eat this for two days, one just having usual pot roast style and the next shredded into burritos.
Alternatively, you can use a can of golden mushroom soup and a package of dry italian dressing mix. You get a nice mushroom gravy.
And don't worry about the cut of meat. I buy whatever is on sale that week. Sometimes it's 2 for 1 at our market. The longer you let it cook, the more tender it will get. Check it after 6 hours though.