First things first, if you're literally just stepping off the retard/casual boat
>always use 4 different type moves with coverage against different types (flamethrower, air slash, u-turn and dark pulse) instead of several different situational moves of the same type (flamethrower, fire spin, fire blast, overheat)
>occasionally certain pokemon should give up coverage moves for situational or support moves (u-turn, protect, calm mind, etc)
>always switch out if you don't feel comfortable fighting whatever you're up against unless of course you need a safe switch, then you should let the pokemon die
And finally for actual teambuilding advice
>begin with 6 of your favorites, no matter what tier they fall into. Play a couple matches and take note of what weaknesses the team has and which pokemon you have trouble with in general. Make changes to the team composition to cover obvious weaknesses (instead of having 3 rock types, mix it up and grab a water or psychic to counter ground or fighting types,etc) If you're playing on wifi you will need several counters for common Overused Pokemon or you wont make it very far. If you're just going to play on a simulator I recommend starting in UnderUsed or NeverUsed as there are smaller threats and less cheap bullshit to deal with.
