VFX Stock Footage elements - where to find good affordable stuff? 
You might be looking for material for that 'blockbuster action sequence' you intend to make, but you don't want to buy a fog machine for the smoke, and you don't think it's safe to lace the set with actual explosives and blow it up, burn it down, or whatever. I hear you - that stuff is dangerous even when you take as many precautions as possible. Frequently it's cheaper and safer to use stock media that fits your purposes. But where will you find it? Well... 
Here are a few affordable Stock Footage effects sources I've found through a bit of digging. You can probably locate others but these are cheaper than average: 

My own stuff, which is decent quality-wise, dirt cheap, and vast in scope. I've got 75+ 3d assets, 150+ video elements, 1450+ image texture maps... across five collections on matthornb.itch.io.



I strongly encourage you to take a look not only at my stuff but also other peoples' for comparison purposes. 
For example: 
Run by Bob Forward, who I've bought a lot of stock media from and chatted with in the past. 
-Looks promising. I got a couple clips from them recently and had no problems. 
-I use the Action Essentials pack fairly regularly. It's good. 
-Again, a ton of really nice stuff. 
-I think the lens effects are good and the other stuff maybe decent. 
-Haven't bought from here, cannot vouch for it but it did show up in searches. 
Again, haven't bought and can't vouch for them. 
There are also a lot of stock texture maps, and stock 3D models you can use in your vfx sequences. One of the bigger examples of a stock textures/3d shop is Turbosquid, but there are many, many others and a lot of them have some free stuff as well.

The banner links at the bottom of each page include links to my own webpages, links to my storefronts/shops online, and occasional links to other [third-party] verifiably legitimate stores and services I've hand-picked, vetted, and used myself. 
That said, I'll openly disclose that when you buy something from another vendor using these links, for example, a link to Amazon.com, I will get a small fraction of the sale amount and will use that as a means of supporting and expanding the projects I'm working on here. These ads for other vendors, as well as - especially! - links to my own shops, are helping me keep these sites online and growing with new content on a more frequent basis.