I'm no rocket scientist, but I've been reading up on some basic concepts of rocket science (including some great talks here). As far as I've gleaned, there's two extremes of rocket thrusts: high speed/low mass (like ion engines) and low speed/high mass (like chemical rockets). While an ion engine, fer instance, could get you going really fast in space, it doesn't have the mass ejected to lift you out of a gravity well. A chemical engine can do that, but unfortunately requires a much higher mass of fuel to be taken on the trip.
My hypothetical scenario for my fictional world is spaceships equipped with ion drives (or similar) for space travel with most never intended to land on a planet. Those that are, however, (like shuttles or my hero's small trader ship) have an additional set of chemical rockets to do the landing and taking off from a planet's surface.
My question is, is that an efficient idea? In very broad strokes, could there be a saving of space and fuel by having smaller rockets and fuel just for gravity evolutions and the more efficient engines for space? Or is space travel such a non-thing compared to the power needed to lift off, that you might as well use the chemical rockets in space too?