What the others are saying. There are a huge number of possible ingredients you can use, an infinite number of variations in the amounts of the ingredients, and so there are no standard proportions. Do you want a heavy cream, a light moisturizer, a medium textured lotion? Do you want a powdery feel upon dry-down, a greasy feel, or somewhere in between? Do you want a non-oily product or one packed with oils or butters? Are you okay with silicones and other "non natural" ingredients or do you expect your products to be "all natural" (whatever "natural" means to you)? Are you willing to use preservatives and chemical emulsifiers (absolute requirements for safe, stable lotions) or do you expect to make a lotion without either of these ingredients?
Susan at swift crafty monkey is the go-to person to learn more about this.