Expectancy requires a trading strategy
One of the benefits of calculating trading expectancy is that it forces you to define a strategy. The strategy goes well beyond the number of trades that you expect to win or lose. You need to specifically define your risk management and stick to the plan to reach your trade expectancy.
Regardless if you are planning to use an automated strategy or a discretionary strategy, you need to plot out how much you plan to win on average on each trade, and how much you expect to lose on each trade.
The best strategies start with determining risk. Once you decide the most you are willing to lose on a trade or strategy, you can then work out how much you need to make to generate a successful trading strategy.