Educated ways to simplify/substitute recipes
There’s no such rule, but you can approach in a strategic way.
You need to know, however why that ingredient is in the recipe. 

When it’s only about flavor (say spices), i think it’s fairly easy to substitue with what you see fit. 

But this is not always the case:

Say your ice-cream recipe calls for a banana, it’s not only there for flavor, but also texture. You can not just replace with any fruit, banana is used there for its starchy texture as well. You’ll need to replace the banana with similar amounts of starch (or eggs that would give a similar texture) and a flavor you see fit.