Battle Of Hoenn Team Building?

[MckinkyMcormic]

i'm trying to get a team up before the tournament this january, and i'm lost as to how to strategize. since you only get to use 3 pokemon, i've found that attacking with the same full team strategies dont work, as i usualy have a stone thrower to boom and a good power-up cannon, but after some battles on showdown i'm seeing that not only is that a costly method, as it wipes out a third of your team, but time is very precious, and charging up is wasting precious jabs at the opponent. so far i've only been able to get good use out of a toxic sableye, which is still risky. what are your suggestions/strategies you have for the tournament?