It depends what your budget is, if you can afford coilovers, buy them, if not, springs will do. As for dropping it, what do you want? To have a car that looks good or handles well? If its handling, I'd only go down by 30-40mm (and to be honest if you can only afford springs this is as far as I'd go), if your going for looks then I'd say 60mm, but on coilovers