What is the purpose of two cell divisions in meiosis?
For developing a 2N cell, we need a N cell from each parent. In any division(meiosos or meitosis), chromosomes are doubled at first. In firs meiosis a 2N cell in divided into two N cells and as you know these N chromosomes are doubled( 2N chromatids). In second meiosis a N cell is divided into two N cells but this time chromosomes are not doubled(in fact N chromatid cells) 
1.Firs division in meiosis is needed because we need N cells to combine, if they are 2N the result of recombination is a 4N cell.
2.Maybe your question is: why a 2N cell is not directly divided into two N cells without doubling? the reason is same in mitosis and meiosos, it is because of a stage of division as you know it is called anaphase in which a kind of protein, connects centromer to centriol, this stage is needed because we need one chromatid of each chromosome in each cells so if this part is not done there is no guarantee to have all N chromosomes in both cells and in fact a kind of distribution is made.
( I hope that I could understand you, well.)