There are lots of systems and useful stuff on how to develop your own systems at profitablebetting. However, you have to join to see all the content but there is some free stuff that is worth a look. flatstats is also another good site for system buffs. betwise is also a decent source of data for developing you own systems and raceform interactive and proform are also good sources of data. hope this helps. I’ve loved developing and running systems down the years. And it can be very profitable !