in fact, you don't have a standard ratio because this one depend of numeros parameters like the nature of the plant materials, the type of solvent you (aqueous or organic) use, the kind of molecules you want to find in the good quantity and the method and apparatus you use .i t will necessary you precise what is your case.
What is the mass of your crude extract?. What are the separation techniques available in your lab. and what are the compounds from previous studies or get from the family from Literature search. The larger the amount of solvent during maceration the larger the amount of material obtained. So it depends on what you want and the separation techniques. For column chromatography under gravity you can use about 15 L for 2Kg of material for maceration on a large scale and the volume of solvent may vary with the availability of HPLC etc.