Hi and welcome back RaitonGian
Since its obviously its been a while since you last visted DA check out the guide to familiarise yourself.
http://www.duelacademy.net/h9-da-guide
In regards to cards and how the game had changed look at deck discussion section here http://www.duelacademy.net/f58-deck-discussion to learn about current decks / cards and give the official rule book a read since there have been some officalls rule changes over the years, That can be found here http://www.yugioh-card.com/en/rulebook/
Feel free to contact a member of are staff if you need anymore assistance