Protective clothing for circular saws?
I'd suggest ear protection, eye protection, and if you're doing a lot of cutting or particularly sensitive to sawdust, dust protection (p95 or better). Steel toe/steel shank boots are generally good on a worksite, but they aren't specific to circular saws.

If you are worried about cutting into your legs or worse, you need to think again about how to use a saw. Seriously. It would take a lot of bad technique to hack into your leg.

PS, circular saw blades don't fall out in use unless you've set up the saw distressingly wrong.