The Polish sentence has two negations: "nikt" (nobody) and, required
by the Polish grammar, negation of the verb "nie lubi" (does not like).
English sentence requires just one negation to have the same meaning.
Once you use the word nobody, you do not need to negate the verb:
Nikt mnie nie lubi - Nobody likes me
The basic form for singular 'you' is "cię". You use "ciebie" when you want to emphasize the pronoun, so it's kinda like "Nobody likes YOU". You'd use it in contrastive sentences ("Lubię Martę, ale nie ciebie" = "I like Marta, but not you" - "cię" would be just wrong here), you also need it after prepositions (To dla ciebie = This is for you).