I started getting into 2s and normal clears around 580.
Look for normal raid groups on the fuller side since they’ll usually already have their 700+ op people in the group, they’ll take anyone max level; and keys with 2 people in them since they’re looking for warm bodies more then anything til a ~10 in my experience.
>10 and heroics raids i think look for 620 ilvl usually.
Mythic raid i haven’t gotten into but I’ve seen advertisment starting as low as 650.