making a new market

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.

for instance, if a market on a rugby match offers 16 point start to a team and i want to offer a 20 point start.. is it possible for me to do that?

phone betfair helpdesk and they may add the market for you