To set your CPM Optimisation Goal, you should look first into what market(s) you are advertising to, but also keep in mind that it's not the only thing that may affect your CPM value.
CPM values may be affected by different factors:
segments (limited product categories),
geotargeting (targeting countries, regions, or cities)
whitelists (allowing only specific domains to publish your ads) or blacklists (blocking specific domains from publishing your ads)
season/period of the year
devices (desktop, mobile, or tablet)
sensitive categories (e.g., gambling or dating)
action supply (how available your target is in a programmatic environment)
Our minimum CPM goal recommendations:
Recommended CPM goal value
If you plan to target multiple markets, you should choose the highest minimum CPM goal value of those markets.
Note: The AI will look for lower prices than your set goal. A low goal will only limit the campaign.