The best soil for Alocasia Sarian is a mix of perlite (a type of volcanic rock), peat moss, and/or compost. As well as providing plants with nutrients, these materials ensure good airflow and drainage. A spongy soil with plenty of organic matter will help keep the roots happy while also helping prevent rot from occurring in the potting mix.
If you do not want to use a commercial product, you can make your own by mixing 1 part peat moss with 1 part perlite or vermiculite and 2 parts light soil (such as compost). This mixture will provide enough nutrients for healthy growth and root development without being too heavy on the plant’s roots.