This page contains the list of all the finished Realmgard stories. Although the links provided are to American Amazon (for the sake of simplicity?), they are available on most, if not all, regional Amazon websites.
There’s no particular order in which to read them, though some stories do make fairly minor references to things from earlier stories.
Expect this list to grow as more stories are finished and become available.
Fryte’s Gold, featuring the Sisters Darkstone.
Physical paperback: https://www.amazon.com/Frytes-Gold-Realmgard-J-B-Norman/dp/1521422540/
The Treasure of Oake Island, featuring the Sisters Darkstone.
Physical Paperback: https://www.amazon.com/Treasure-Oake-Island-Tale-Realmgard/dp/1731162839/
The Bandits of Goldharbour, featuring the Sisters Darkstone
Physical Paperback: https://www.amazon.com/Bandits-Goldharbour-Tale-Realmgard/dp/1689431911/