The most important community contributions that you can offer are Solutions Authored. This means that you wrote a reply on someone's thread and they felt like your reply was a valid solution to the issue initially addressed by their thread so they marked your reply as the Accepted Solution. That is what we are mostly here for, after all, working solutions to our issues! Replies Authored, Kudos Given/Received are other examples of community contribution, but they will not be weighed as heavily as your Solutions Authored!
There are lots of threads throughout the PowerApps Community right now that don't have replies or haven't received any acceptable solutions as replies. This is something we can all help solve together if we offer our knowledge wherever we can.
Another major contribution is adding to our community blog and galleries.
How do I find the topics/threads that I can offer help with?
Let's say that you have some knowledge and experience regarding using the "Compose" action in PowerApps. You can use the search feature to conduct very specific searches regarding the "Component" action that will only show the threads where you can offer help regarding that specific action. This is an excellent way for anyone to help lots of other PowerApps users while at the same time keeping your skills sharp and learning new things! I recommend that EVERYONE registered here on the PowerApps Community regularly conduct quick searches for the areas where you can offer insight. I can almost guarantee you 100% that you will at least learn some great new things along the way.
Are you curious about how you could be giving back to the awesome PowerApps Online Community?