Are the primary TLDs taken by other marketing-related companies? So any of them hold the trademark in your country?
In terms of SEO and brandability, any TLD is perfectly fine. COM is a must if you're relying on word-of-mouth or type-in traffic, but people almost never look at the TLD in Google searches or webpage/email links.
What kind of sites are on the com/net/org variations? Are they related to marketing in any way, or are they entirely unrelated to your business?Just a cool name, no trademarks yet!
Domains the just parked, not in use!What kind of sites are on the com/net/org variations? Are they related to marketing in any way, or are they entirely unrelated to your business?
If there is any possibility at all that your chosen business name could mislead people into thinking that you are part of a previously established company, you will almost certainly lose the domain.
Find an original name and get .com and .io if you really want IO
If you're buying IO cuz the .com is taken, it'll look cheap.
another would be .agency but .IO has its own charm from my POV.if your name of seo agency is interesting you can use .marketing
for example: interact.marketing, helpmy.marketing, etc...