I've always been one of those women who are wondering why we should use a toner after washing our face, isn't it pretty unnecessary? Not at all, let's see why.
Soaps and cleansers have basic formulas, while our skin's PH should be around 5.5, depending on the zones considered. If our face's skin was normal, it should be around 6.5. Instead dry skins have a more acid PH and oily skins have a more basic one. That's why with cosmetics (or simply a toner in this case) we might be able to balance our skin's PH.
MY FINAL ADVICE: you don't have to look for expensive toners, which will probably contain alcohol (for its atringent properties), just use floral waters and empower them with an essential oil of your choice, you'll let me know then!!