I have to write on (1) my reasons for pursuing doctoral studies, (2) personal objectives, and (3) career plans. The last one is straightforward. The first one: have done some research and liked it very much, have a solid quantitative background (necessary for a PhD in Finance) and feel I can do well in an academic career.

The second topic (personal objectives) sounds rather repetitive to me (a hybrid of topics (1) and (3)) so I basically do not know what else to write in this regard. Please help.

perhaps you could interpret it as "things you want to achieve on the personal level". then the first is "why?", the second "what you want to achieve on the personal level" and the third "what you want to achieve career-wise".
examples could be: develop as a researcher, learn about the deeper mysteries of statistics as can only be done in applied research, achieve a fundamental understanding of the research process and of the topic - or even, more personal - learn about your strengths and weaknesses, what drives you, how much you can achieve... (i'd stick to the more general "personal" objectives though)

Yes, you are right. It also happens that those things to achieve on a personal level appear in most sample essays I´ve seen on the web, and I´m afraid my essay wouldn´t look so "unique". The question would now be, how to make those objectives unique and stand out of the crowd?

hm, that's hard
i would start thinking from the centre - you. what is it about you that makes you special, unique (or rather - what are the personal things you want to achieve which are very important to you? is there something that you want to achieve that is special?) most likely the special-ness lies in the combination of several things, rather than just one single aspect.
in general, i think a personal statement that is based on some real introspection will sound more convincing than "copied sentences", all by itself.
good luck!