What would your top tips be when creating impactful, easy-to-understand data reporting dashboards?

Focus on easy to understand, impossible to misinterpret content instead of colours.

For reporting dashboards, three things to keep in mind: decision makers, their expectations and action-driven outcomes.

Decision makers - The dashboard is a decision support tool for them, making their job easier. We need to present the information and insights in the way they are most comfortable with. So make a conversation with them as early as day 1, show them samples, and tweak the design based on their feedback.

Expectation management - prioritisation of changes/ new requirements with notes on any gaps/ roadblocks/ uncertainty/ dependencies

Action-driven outcomes - lead constructive conversations with decision makers and relevant stakeholders over the "expected actions" to drive "desired business outcomes". Then document it and get the sign-off and endorsement from decision-makers, to embed it into the dashboard. Executives love to see their decision driving real tangible outcomes.

Great comments thus far, just want to add a note about accessibility.  When creating dashboards keep in mind some audience members may be color blind, you'll need to also include alt text if you are using red, yellow, green etc to visually indicate whether the metrics are favorable vs unfavorable.  

Make sure you keep an eye on the audience; whatever you produce needs to be suitable for them.

Then consider requirements from a technical perspective, then effort and finally training.

Also monitor usage after you have made it available. 

In my opinion, If the ask for the number of elements of the dashboard go beyond single digit, it means that either a) it needs to be a report, and not a dashboard
b) they need to be separate dashboards

Irrespective of the audience.