As in any airplane, the max range speed is the speed at which you'll burn the less fuel per NM. In still air that is the best lift to drag ratio speed. In the 146/RJ series it's Vfto + 30 kts. You'll have to fly faster if you have headwind and slower in tailwind.
Now the standard Long Range Climb / cruise speed is 235 kts which is a good compromise between fuel burn and time. Typically it's only 1% more fuel burn but a lot of time less.