How to create Social Media Assets with After effects?

I think Shape Layers make for good reuse of assets - they keep file sizes down and mean you don't need to have separate files with images.  And if you convert any logos into paths / masks either through autotrace or illustrator - then that's even less overhead.  Also stick to common fonts, otherwise people have to go hunting for them and half the time, those fonts come with a price tag.

I find Adobe Stock provides excellent inspiration, although that's for personal projects.  I'm not sure what the rules are for creating assets intended for sharing if they contain someone else's resources.  Normally this is not allowed, so you might want to check first.