Dracaena marginata plants prefer medium light, but survive in low light situations. Lower light slows down the growth rate and reduces the size of new leaves. Direct sun burns the leaves.
Over-watering causes root-rot and is the main reason a Dracaena marginata dies. Water well and don't water again until the top 50% of the soil is dry. In low light, this could take up to three weeks. Brown tips on the leaves indicate over-watering or too much fluoride or salt in the water.