None. It is irregular.
Nom = ego
Genitive = Mei
Dative = Mihi
Accusative = Me
Ablative = Me
First/second declension. It can be Latinus, Latina, or Latinum.This is because "Latinus" is an adjective, the name of the language is "lingua Latina."
Ego IS a Latin word. It is the Latin for I.
Fifth declension.
I.