Suggested by an LC regular, copying someone's team actually helps out a lot in learning much more about the metagame but also the synergy behind it.
What I like to do is have several goals that I can accomplish without having them clash together. One example of good synergy is found in Heysup's teams. He uses a MixDour/LO Gastly offensive core. He focuses on pulling off a Scarf Bagon sweep but what stops it? A main culprit is Bronzor. MixDour is already hard to switch into so using Bronzor as a switch in helps lure in Pokemon such as Munchlax/Gligar who counter/check LO Gastly. The opponent is left to decide whether to switch or not. If they switch they might open a Gastly sweep. If they stay in Bagon will have a field day with Outrage.
It does take a while to understand the synergy but in time it gets more understandable. What exactly are you using? I can battle you sometime and see what I can do to help.