It would seem that there are two goals in this event...
Win when attacking. This should be straightforward if you have at least three reasonably leveled cards with the same attribute.
Win when defending. This is substantially less straightforward, as its a mixture of getting players to attack you, and having a set of cards that is capable of winning despite the information the player has when choosing who to attack.

The information given... center card, rank, and attribute (moe, sexy, babe, none) is enough for a player who has leveled three cards of a single attribute sufficiently to only choose battles where they can win (unless no battle is available as a choice). So I'm really not sure what the best strategy for defending is... choosing a grouping without an attribute has the best chance of winning... but likewise seems like it would deter players from attacking you, which isn't desirable...

*shrug*

*edit*
Actually I made a mistake in reasoning there, you need a full set of 5 cards sufficiently leveled if you run into a *trap* deck, since in that case every you need to win all of the matchups where your cards have a strong matchup.