Looker Studio allows you to manipulate your data as you wish, you can explore and display in multiple ways !
One thing that can be frustrated is to add some metrics from different data sources, but there is a simple way to do it !
Follow these steps to add 2 metrics from different data source :
There is an easy way to blend 2 data sources : select 2 components from 2 different data sources and do a right-click then Blend Data.
Here is an example of the investment in Google Ads and Facebook Ads :
Once your blended data sources is created, you have a new component in your report. You need to modify the formula and type to get your sum.
You can now select the new component that appears when you create the blended data source. As you can see, Looker Studio try to divide one metric by the other, but we can modify the formula so instead of having this :
We will do this :
And we will modify the type from Percent to Currency (Euro) :
And you are ready to go !