Goals and why they're so important

If you have an idea about what you want to do with your deck and how you want to make it roll, then you should build up your deck that way, I must addmit that it can be a pain to have to buy packs and not get the ones you want.
Here are some examples of decks:

-The Blackwing Deck wants to be aggressive with superior Special Summon effects; control the Duel with Icarus Attack and Blackwing – Kalut the Moonshadow; and take advantage of Dark Armed Dragon and Black Whirlwind.  It wins by overwhelming the opponent with attackers and control cards.

-Scraps want to get Scrap Beast to the Graveyard as early as possible; Special Summon it with Scrap Chimera to make Scrap Dragon over and over; and clear the field of monsters to make big, direct attacks.  Scraps win by repeatedly Summoning Scrap Dragon, attacking hard and fast.

-The X-Saber Duelist wants to block early attacks with cards like XX-Saber Emmersblade, XX-Saber Darksoul, and XX-Saber Fulhelmknight; build their Graveyard to take advantage ofXX-Saber Faultroll and Gottoms’ Emergency Call; and threaten the opponent’s cards withXX-Saber Gottoms and XX-Saber Hyunlei.  X-Sabers win with strong defense that buys them the time to make deadly combos.

Some awesome offset cards are Black hole, monster resurrect and, book of moon.