It depends on the area you need to illuminate, your terrain, the effect you'd like to achieve and the beam spread of the fixtures you select. For example, our Max Spread path lights produce roughly a 16-foot diameter beam spread. For continuous illumination along a flat path, they'd be spaced about 16 feet apart. For independent pools of light, they'd be spaced about 20 feet apart. On the other hand, our Mushroom Mini path lights have an 8-foot diameter beam spread. They'd be spaced about 8 feet apart for continuous illumination along path, or 10 feet apart for independent pools of light.
Bear in mind, a fixture is generally placed very near the beginning and end of the path. Let's say you're using the Max Spread on a 50-foot path; you'd add 16 feet to account for the two beginning/end fixtures, because half of their light will extend beyond the path. The 66-foot length divided by a 16-foot beam spread would 4.125 fixtures, which you might round up to five. Or for the Mushroom Mini, you'd add 8 feet. So, 58 feet divided by the 8-foot beam spread is 7.25 fixtures, which you might round up to eight.