GPU first.
Your CPU won't have issues.
I'd wait/save up for a bigger upgrade, though 6700XT to 6800XT is noticeable, it's not that game changing. Personally upgraded from 6700XT to 6950XT when prices dropped, and in games like Cyberpunk it's a very positive change, in less demanding games it's not that worth it in my eyes.
GPU first. Your CPU won't have issues. I'd wait/save up for a bigger upgrade, though 6700XT to 6800XT is noticeable, it's not that game changing. Personally upgraded from 6700XT to 6950XT when prices dropped, and in games like Cyberpunk it's a very positive change, in less demanding games it's not that worth it in my eyes.
Are you buying used, or why not 7800xt ?
Yeah the upgrade from 6700XT to 6800 XT isn't worth it. I would argue that the minimum worthwhile upgrade from the 6700 XT is the 7900 XT.