Red Ash is a core rules system, meaning it is designed to be a foundation for a larger system. I designed this Red Ash for my own game development plans. By making these rules available anyone that wants too can design their own game world to enjoy with their friends. I only ask that you respect the license and do not sell it. Additionally, I would also like to hear back from you and your experience with the system; what works, what doesn't, what needs adjustment.
Designing a world will require that you spend some time planning. I do not think it will require that you make every mountain, river and ocean but you can start with a small city. A city quest can in some ways be easier to build as you do not have to have as great mix a creatures. Let the players know what races and classes are available. Then build the adventure around that.
All maner of quest can be had in a city; Missing Persons, Clearing the sewer of infestations, Stealing a artifact from a collection, or even tracking down the ones who did. Add a little spice to your adventure with NPCs (Non Player Characters) that have different attitudes towards the adventurers. And even include weather for atmosphere.
Red Ash comes with predefined playable species but you can build on top of or in addition to those listed. If you want to limit the playable races, but still have some variety make sub-species or races of one or two playable species or you can make one species with different races.
Everyone has a past but it should not come up it casual conversation unless a player character interacts with or overhears an NPC.
As a people we also all have a shared history that is often tainted by our own opinion, ego and agenda. Somewhere in all these stories is the truth of a matter.
The peoples that populated your world should have a shared and personal history too. Shared history is one of those things that as a group bind a people together. Sometimes this binding traps us into a narrow point of view that is simply accepted and drives us in an endless repeat of past events. History can be bittersweet that way. Other times a people learns the harsh lessons of our mutual limitations.
Designing a gaming world has its own rewards made manifest when the players interact with it and become engrossed in the story.