need help switching soils

ok heres my question. my friend gave me a plant (dont know what it is) but it was in a small pot about 4"x4"x4" the plant has been under light for almost 2months now and its not getting any bigger its about 7" tall and bushy ass hell and well i want to transplant it to a bigger pot but!...i want to know if switching soils will harm the plant since i dont know what kind of soil(brand) its currently using. what do you guys recommend?

anyone??.....

still anyone???

I use equal parts of perlite, peat moss both not miracle grow, and mushroom compost. I Add 1 tablespoon of lime per gallon of mix and there you go. You need to use some water soluble nutrient too... Stay away from time released nutrients and pre fertilized soil!