You are innocently asking a question for which people get slaughtered on fora
Substrate is heavily debated and depends as much on your local conditions and the care you can provide as it depends on personal preference.
In geneal: Soil needs to be able to let are in and out so the roots stay happy. If you have plants in a very rainy location you should avoid any type of regular potting soil, and only work with coarse materials that let water go through in seconds. (See also www.growingbonsai.net/characteristics-of-good-bonsai-substrate/).
That being said.. If you have a regular IKEA ficus type bonsai you can do with any good potting soil, as it gets treated more like other houseplants than as a bonsai. And yeah, cactus potting mix (Which may vary a lot from producer to producer!) may work fine.
I know this does not help you much. Perhaps you can tell us what you ave there (Or show a picture) and how you keep it. Then .. maybe a better answer can be given.