I read on some forum that Spain was willing to sell Equatorial Guinea? No idea if that was true (it was a wank thread about WI the richest American was of Polish origin and left all his money to Polish state, and what they could do about it).
So assuming that rich uncle from America gives Poland so much cash it doesn't know what to do with it, and the Spanish are indeed willing to sell...
With such a small colony it would be basically nothing happens until WW2, when this is where Polish government, gold reserves, and civilian refugees begin moving in - although it would be a rather poor place to be, tbh, especially initially. Later on it could become Polish micro-Taiwan. With Poles possibly outnumbering the locals, and large number of single men which would have to lead to mixed marriages, it would avoid decolonization (especially as these men have plenty of military experience). It would be rather poor place at least until the oil is discovered (although if the Government in exile refuses to send its gold back to the homeland, things might become more interesting)