Improvement comes through practice. I wouldn't recommend duel mode for practice as Kate is very unintelligent and unrealistic for what you'd get out of a human opponent.
The more experience you gain using particular clans the better you will understand how to use them, as well as how they're likely to play against you.
The same applies on a non clan-specific level. The more you have to try and read/predict your opponents plays in certain situations, the better you become at making the right call.
Perhaps making a good half deck with your Pussycats deck and then supplementing the other half with whichever clan you wanna try out with somewhat similar cards can be a good exercise?
personally i find Pussycats are so versatile in half decks due to their utility, so they could go with just about any clan.