Seems like you are confusing solubility with amount of substance dissolved.
Adding more water doesn't make something soluble. Solubility (typically expressed in units like g/100g of solvent, or equivalent) is an intensive property, doesn't depend on the amount of substance.
However, assuming you take the same amount of several substances (say, 1g of each), the less soluble substance is, the more water you need to dissolve the substance completely. It doesn't mean it got more soluble, amount of substance dissolved is an extensive property, it depends on the amount of solvent.