If you have trouble with lumpy gravy try using granulated flour. It's a nearly fool-proof flour because instead of perfect dust its tiny grains of wheat flour. If you rub it between your finger and thumb it feels like grains of salt. It comes in a cardboard canister like powdered creamer and sugar for coffee.

If your gravy is too greasy try to skim the grease off the drippings so you can use the meat juices without so much grease, then cook the greasy juices till they start to brown up in the pan before adding the flour.

If you need gluten-free gravy use instant gravy mix or cornstarch, but use meat drippings and broth instead of water to give a better flavor.