Hey Juten, If you would like some tips from the designer I have a few :)
The items are best used when you can get max value out of them and save the most amount of hp loss. Most ignore the traits too.
The more you play you may notice you use a lot of a certain weapon power early on and you will have a better feeling when pushing your luck if you will pull them later when you need.
Lastly it's balanced so that you cant play too safe and you cant push too often, got to find a good balance.
That said it is push your luck and sometimes luck is not on your side - my win rate as the designer is about 85%.
Hope that helps and thank you so much for giving my game a chance!