A deck with two clans is usually what is done. Have a look at some of the many other "I need help making a deck" thread s to
see some people's ideas about good clans. I've found that the best players I've played against have used Uppers/Sakrohm
decks. The bonus is very important here, and bonuses that effect the outcome of rounds (+ or - attack or power), rather than
damage TEND to be more useful, but you can have success with either.
I wouldn't see buying a card with less than 5 power a viable option unless they had a really good ability. Mostly you want
cards with high power and good abilities. Graksmxxt and Jackie are good examples of these. You'll also be able to tell
particularly good cards because they will be expensive in the mall - like Zatman, who is only uncommon, but is priced higher
than many rare cards.