Finding assets for After Effects

Pros and amateurs usually create their own content. Stock Footage is sometimes helpful for filling in something you can't create or shoot for yourself. I have about 2500 24 MP or larger background still images of city streets, alleys, mountains, clouds, old buildings, mountains, and other things I have shot over the years. I use them in Photoshop and After Effects composites when I need set extensions, need to replace backgrounds, or replace the sky. On some projects, I have to search the Stock Footage libraries, but I've been doing this for a very long time, so I have a lot of my own assets.

My graphics are almost all created in Illustrator because vector images can be scaled without problems, and sometimes Photoshop. I make my 3D models in Blender (powerful, open source - free, with lots of tutorials and a great community) and import them into After Effects using Element 3D or C4D. I also use C4D to create 3D models. 

I don't know what you are looking for, so I can't point you to a site that might have the images you want. Stock photo and video prices run from free to several hundred dollars per second. Just grabbing an image from Facebook, Instagram, or the web can land you in hot water if your videos are seen by more than a couple of people and get you in really big trouble if you sell the video or sell anything else with the copyrighted material.

I have used images and videos I shot with my cell phone as parts of the composites I have done for some major clients and even used an iPhone panorama as a sky replacement in a shot for a feature film. Keep your eyes open, always carry some kind of camera, and start collecting images, then fill in what you can't get using stock photos, graphics, and footage. If you ever plan on selling anything with your videos, make sure you get model and location releases.

There's tons of alternate sites to get content like Envato, Pond 5, Getty Images and whatever else may be atround these days. Outside that of course the point is pretty much to create your own content using AE's native generation tools liek text and shape layers or effects plus using all sorts of other programs. That has always been the case with motion graphics. You can't just settle on learning one program like AE. You definitely will need to learn Photoshop, Illustrator and a 3D program alongside at least. Most artists in this field use around seven programs and in addition to the base tools have invested in padding out those programs with additional plug-ins, scripts and so on, downloaded additional fonts on their system, have built a library of stock content and past projects containing reusable assets. That's just how this works. You can't expect to be perfectly set up overnight. That said, and I don't mean to be offensive, it seems to me your biggest issue is that you yourself don't quite know what you actually want and get lost in a sea of digital content without knowing what you're looking for, so maybe you should take a step back and conceptualize what you intend to do with pen and paper and then strategize how and where to get/ produce the individual assets.

Mylenium