In the language of Polandball comics, it means "give land/territory".

"Gib" is taken from the German imperative for "give!"

Best theory is that "clay" as "land" originates from a bad machine translation.

It seems somene created a Wiki that covers these terms: https://www.polandballwiki.com/wiki/Terminology#Clay

"give clay". The Dutch wanted to have clay for their world famous clay baths...

Give land/territory

After rereading multiple times to understand it, i think it means the small blob wanted land so "give clay", the other big bullies didn't want to contribute, so started taking from the sea.