Hi @daniellemaree85 ,
Does the goals, opps and clients List have same data structure?
Do you set up a relationship between your three SP Lists though fields?
Further, do you want to connect a single one Gallery to multiple SP Lists?
Currently, within PowerApps canvas app, a Gallery could only be connected to single one data source. If you want to connect one Gallery to multiple data sources, I afraid that there is no direct way to achieve your needs.
I assume that you have set up relationship between your three SP Lists through fields already, as an alternative solution, you could consider combine your multiple SP Lists into a single one collection based on the relationship field (e.g. LookUp field).
The user Moores35 has faced similar needs with you, please check my response within the following thread:
https://powerusers.microsoft.com/t5/Building-Power-Apps/Gallery-displaying-data-fields-from-multiple-lists/m-p/171515
AddColumns function, ClearCollect function
If above solution is helpful in your scenario, please consider go ahead to click "Accept as Solution" to identify my reply as helpful.
Best regards,