Ya, I saw your little Irish!
Not sure how events are run in Portugal, but different events here would have different requirements for qualification. For instance, if you want to do the AKC's official events, you must have an AKC registered dog and meet some other criteria. For less formal events, the requirements would be less strict. So maybe check with obedience groups or breed clubs in Portugal and see if they can tell you what the requirements are and what breeds might excel in the level of obedience you'd like to compete at.