If you have a mac, learning how to get the most out of the built-in Photos app and the built-in iMovie app is a great place to start and its free.
If you have a PC or want to get more advanced, I agree with Lightroom for still images. Davinci resolve is the best non-iMovie free option. It's complex, but there are no better options I know of.
If you just want quick and easy, you can upload everything to Google Photos for free (photos.google.com) and let their Artificial Intelligence edit your photos and movies. It will be 10 times worse that what you would do yourself, but take 1/1000 the time.