Hello -From a new user

[Wildcat0017]

Hey everybody. I'm new to this site, an somewhat new to competitive battling. I play rated battles on battle spot, was just wondering if anyone could give some pointers to me. i have good pokemon by themselves, but they don't work well together. it seems other peoples leads destroy me, but once i get one of them down i can usually do pretty well, but im almost always on pokemon 3 and 4, but if i lead with them the same thing happens. Should i start with two bulky pokemon, or two attackers? One of each? Any higher level general help would be appreciated. Thanks.