The easiest way to find trends is to go straight to the source - channels that are setting trends. I actively follow 50+ leading kids/toys channels, and scan their "videos" page every 2-3 days. You can see trends developing right across those. usually what happens is someone comes up with something (let's say Elsa is pregnant and Spiderman is responsible, or spiderman starts farting and dropping Smarties out his poohole) within 2-3 days other channels will have copied and spun that idea. A week later the idea filters down and channels like us at the 20k - 200k sub level are doing spins on the same stuff. So you can catch the trend withing that same day or two, and if you have all the resources setup (costumes and props) you can get a copy video up matching t/t/d within 24-48 hours and get on trend.
You can use the subscription left sidebar to do it, or an easier way is I have the channels sorted into bookmark folders in Chrome, then right-click a folder and open all links in tabs (which will take you to the videos page sorted by 'recent'). Then tab across and you'll get a feeling for trends. You can also resort everything by the highest view, and see what's above the fold and recent, say the last month or two, that would be pretty viral content.
This is of course for kids channels, I can't comment on gaming I have no experience there.
I do very little off Yt, like trend websites, all that sort of stuff, it's all second derivatives. The pure data is right on Yt itself.
But, what happens with toy channels, is channels start making videos about upcoming movies and toys. A channel I follow went to 1M+ views on their video within 2 weeks on a steep exponential climb as they were one of the first to spin a Finding Dory idea. So you can position yourself before trends with common themed videos like "giant eggs" "play doh eggs" "family fun shopping trip" "surprise toy hunt" just add the toys from the next Disney/Pixar huge movie release.
I looked a the Yt API, but my coding skills are rudimentary, it would take months to get up to speed. There is a bunch of competitor information it would be useful for though....