My current customer has an "IT-Dashboard" basically it shows if a certain application is working or not through various checks.

Unfortunately (as with most bigger organizations) there is no actual "Performance Dashboard" or something similar for DB Servers. I'm currently in the process of establishing the collection of such Information - you gotta start somewhere, right? I'm looking at basically wanting to have a mix of PowerBI (for Presentation) with SSIS Execution metrics (this is a BI Environment after all) paired with information like DB Growth Charts, Changes in Execution Plans over time etc. but it'll take a while (being the currently only Dev on this part) until I'll be able to present useful "IT decision making" metrics to let's say the CIO so he'll much more likely approve the addition of resources like CPU or RAM in a much shorter time.

Throwing Hardware at things that are already unusable isn't the challenge here, it's preventing things to get there.