Analyse a set of data

I have designed and have been testing a system of gambling on horse racing. I want to work out the following. 1. Given the sample size, how reliable is the data in terms of standard error, confidence level etc. 2. Will a larger sample size make a material difference to accuracy of the data over a longer period. 3. Make any other statistical comments over a doubling of the amount bet, and how that would affect the risk. 4. Any other general suggestions/recommendations in relation to the data and how it may be improved. I expect a document with comments that will assist my strategic plan from a statistical perspective. Thanks