If a person performs his ebadat without following a Marja'e...
If a person performs his ebadat without following a Marja'e then his actions are considered void. The only exception to this is when he decides to do ehtiyaat. Ehtiyaat may arise in the situation where one mujtahid is of the opinion that an act is haram and another disagrees. The ehtiyaat in this case would be to avoid the act all together. If one is unable to perform ehtiyaat for any reason then one must follow the Marja'e.
Outside of ehtiyaat, any ebadat a person performs without doing taqleed is considered nullified unless he is absolutely sure that he has performed in correctly and according to the fatwa's of the marja'e he was supposed to follow. Kinds of Taqleed There are four different kinds of taqleed that can occur: A mujtahid following another mujtahid. An ignorant person following another ignorant person. An aalim (mujtahid) following an ignorant person. An ignorant person following a mujtahid.
The first kind of taqleed is not allowed. By definition, a mujtahid must have enough Ilm at his disposal to be able to understand all the required articles of faith and derive solutions about them if needed. If a mujtahid is so unconfident of his own knowledge and decisions that he finds it necessary to follow other scholars then he is not fit to lead the general ummah. The second and third kinds of taqleed are only destructive and must be avoided at all times.
It is this kind of blind following that led the idol worshippers in the ancient times to tell the prophets sent to them that they would continue in their shirk simply because their fathers before them had done so! It is worse when an aalim, who can tell the difference between right and wrong, finds himself so blinded by the world that he follows its ignorance.
When a Muslim who knows his true purpose in life begins to imitate the ignorant ways of the materialistic world then he is in the third category and is much cursed. The last definition of taqleed is the only feasible option of the four. It can be likened to a sick person who goes to a doctor for a cure. What we would say of the same person if he went to another sick person for help or to a mechanic?
When a person who does not know enough about a certain subject, seeks answers from an expert in the field, he is doing taqleed. In the case of Islam, the Marja'e followed must be both an A'lim (Knowledgeable) and Adil (Just).