Thinking about .5 GB or 1 GB gets you a share in a horse.
Each horse rolls 1d6. On a 2 to 5 they move forward 1 space. On a 1 they do not move. On a 6 they move 2 spaces.
Say a total of 30 GB was bet on all horses. Then say horse number 4 wins. Say person 1 bought 10 shares of horse 4 and person 2 bought 3 shares of horse 4 and person 3 bought 6 shares of horse 4 and person 4 bought 1 share of horse 4. That's 30 GB divided into 20 shares making each share worth 1.5 GB so
Person 1 wins 15 GB
Person 2 wins 4.5 GB
Person 3 wins 9 GB
Person 4 wins 1.5 GB
(-10% fee for gaming commissioner so it would have been 27 GB divided into 20 shares I just didnt wanna do that math)
At the same time PCs can race their own horse for an entry fee. Purse will be entry fee x number of horses (-10% fee for the gaming commissioner)
So if 6 horses entered with entrance fee of 3 GB that's 18 GB purse (-10% so 16.2 GB) that the owner of that horse would win.
Might add in certain bonuses for horses like +1 move per race or 1 reroll per race and maybe roll weather for each race and a horse might get +1 move one time or even 2 times per race if they are a mudder that runs well on a wet track. Horses can be rolled and might have more than 1 bonus which would increase a horses price and open up the possibility of horse raising and breeding maybe but might be too much to add.
Would then post something like below as the race progresses: