Bring the almond flour to room temperature before using and always store it in the refrigerator or it can go rancid.
You can use any type of oil. My favorite is the Chosen Foods Oil Blend. Try sticking to one with a neutral flavor or else you will end up with heavy muffins.
You can use any sweetener of your choice. I have made these muffins with coconut sugar as well as maple syrup and they always turn out good. If using agave syrup or maple syrup add 1/4 cup to the recipe. If using Coconut Sugar, add 1/2 cup oil and a splash of milk to keep it moist.
If you end up with dry muffins, then either you have overcooked them or added less oil.