1. You are not going to be perfect in unseen dictations in 1-2 months it take some time to practice variety of words and phrases.
2. Generally you need to complete atleast 6-10 magazine to be good in writing unseen dictations @ 80 wpm speed.
3. It would be good if you can practice single transcription 10 times (3 times by writing it from magazine and rest by playing recording of that transcription). You can record transcription according to your speed.