My opinion for what it’s worth:
If something fails outright, do some divination to find out why it didn’t succeed, if you keep going there may be a reason you don’t want that thing or why it would be harmful, and some entities could actually be looking out for you by making sure you don’t get it, or don’t get it yet.
Yes, you can “stack” evocation, invocation, all sorts but it’s best done under the auspices of one entity who will then 1. direct you to the entities you need, instead of you trying to choose and 2. command them directly himself/herself, which is more effective than trying to micro-manage the process yourself.
The first one I knew for ages, the second one I’m just learning in the past few months because I never tried to evoke more than one entity towards a task since I was a child, but following on from some of my experiences when I invoked Ahriman I’m seeing different ways of working that include this.
Just my experiences here though so there may be other and better answers.