The first thing you want to do is only invest on positive expectations.

As I posted just recently in another thread here, I classify the race on the Favourite and what was the major factors or combination of major /minor factors that determined that Favourite, then the seperation between it and the 2nd Fav.
I then have my subset of data
Remember at the most we have only about 15 factors for the dogs. and how they punters play each of those combinations is so predictable, I just compile all the past results and I know the avg payoffs or positive/negative expectations for each combination by rank order.

So you would have seen in that race what were the Factors in determining it a Fav.

But as you would have seen in that other thread the gold was laid out, but it was too difficult to do?
Don't keep trying to handicap better, you'll improve .5 of a percent, improve your wagering improve 100%, learn to do your database, compile your results create sub sets of data based on a few Factors,
I know you have spreadsheets to do this automatically

Give up the notion of betting only your top selection (especially when over time its a negative expectation) and your halfway there.