What should I add after a scanner?

I already have a decent professional scanner, so I’m trying to decide what the next useful purchase for the workshop should be. An oscilloscope, smoke tester, battery tester and a few electrical diagnostic tools are all on my list, but buying everything together doesn’t make much sense. I’ve been browsing https://ecutools.eu/ to see what’s available and realized there are far more options than I expected. For mechanics who built their diagnostic setup over time, what did you buy after your main scanner that actually became part of your everyday workflow?

A smoke tester was surprisingly useful for us because it solved a lot more than just obvious intake leaks. After that, I’d probably go with an oscilloscope if you’re doing more electrical and sensor diagnostics. The learning curve is higher, but once you get comfortable with it, you stop replacing parts just because the scan data looks suspicious.