I do not understand much more where the topic sentence of each paragraph is.
In your introduction, you mean there are 2 paragraphs: Ad. and disad.
In each p, you must make sure that you have a topic and some more sentences to suport it.
for ex,
TV benefits people in some ways. First of all, tv brings to us an enormous information about the word up to date.....Secondly, it help us relax......Thirdly,..... . Finally,(maybe, you should include a short, general summary of this p)
However, we can not deny some problems tv have influenced on people. Firstly,......... Next, ...... Then.....The last.....
i strongly agree that the effectiveness of an essay will be increased if the author uses the transition words appropriately.
Hope these tiny kinds of ideas can benefit u in some way.
Thanks for your reading.