I'm not sure what brands you have in America. But, ome brand that I've heard recommended is Alpinestar. Expensive, but again, can't say from experience. But they're quite good from what I've heard.

I wear near enough full RST, I got a trousers/jacket textile suit for about, I think, 320 usd. It has padded elbows, shoulders, and a back plate. And padding at the knee caps. I also have RST boots that extend higher up the legs. And some summer gloves with padded knuckles and leather around the palm and mesh on top. But, my other gloves were chasing really bad sweating.

I don't think the US and the UK use the same safety rating guide. But, as long as you're getting from a reputable brand, and getting protection for the most important parts, you should be okay. So the most important being hands, back, elbows, shoulders, knees, and feet/ankles. Don't use steel capped boots though. As one read those can cause more damage to the toes.

For a very rough price, I think you should aim for about 500 usd for the rest of the gear. Might seem excessive, but like I said, can be the difference between life and death.

Actually, some where i got confused was between textile and leather. But, whilst leather is a lot better as it won't tear as easily. Good textile would be more than enough unless you're going to really be breaking speed limits and going for track days.

here's 2 videos from a youtuber, he knows more than I do.

and the second

Don't worry too much about jumping straight for summer clothing and and cold clothing. Cold clothing will more than likely have thermals you can remove. And, with the exception of being stuck in traffic/at traffic lights, once you're actually moving you should get a nice breeze. And something I love about my rst jacket. Its got titty zips. If its a warm day, open them up, and it allows a lovely breeze to engulf your top half.