How to set up the System Developer

• You should be using proportional staking to test all systems, so that longshots don't have an abnormal positive or negative effect on results. Also, it is better to use the best of SP and three totes to reflect the minimum results achieved as that price is very easy to obtain in the market and you can in fact do better. You can find out how to do setup both of these options in the GTX Manual here
• Focus on thinking about the types of races and horses you want to back and think about asking the System Developer questions to isolate those horses and see where edges may exist. 
• The goal of a system should be to get somewhere close to breaking even from your automated list. Use that as a starting point to then make your final betting decisions on those you want to back (such as the Bet Contender Checklist in GTX).

Considerably more information relating to the setup and use of the System Developer can be found here.