Assuming you are offering money into an empty market on bf, price up all the outcomes to what you consider fair value.
Then add a margin of safety to each of your offers. I wd not actually advise adding the same margin to every runner; consider what is likely to be bet and also instances where your form is questionable given team / trainer habits. You are looking to strike a balance between getting filled at your supposed 'positive expectation' price and finding y/s w/ a lopsided book and on the wrong end of an information disadvantage.
The difficulty w/ market-making in many sports (I only play horses and specials, so you'll need more specialist advice) is that the people who get in b/f you as market makers are often very accurate.
Assuming you are offering money into an empty market on bf, price up all the outcomes to what you consider fair value. Then add a margin of safety to each of your offers. I wd not actually advise adding the same margin to every runner; consider what