The drake is used heavily in 0.0 at the moment for all three roles you have listed. I have seen fleets of 20+ drakes roaming at times, and not many people take them on without bringing exceptional DPS. 1v1 PVP is even possible with a drake, but I wouldn't reccomend it.
The manticore is reasonably good for most fleet things in 0.0, but do not use it as a scout ship - Use the buzzard instead. The buzzard is more nimble and less likely to become the target in a chase when you go through a gate camp.
Stick to your merlins or kestrels to get used to solo PVP in 0.0, advance to the caracal or moa when you feel up to the extra expense, then move into HACs like the cerberus and eagle when you are overloaded with ISK. Once you are using HACs for PVP, you should be able to use them well in ratting and plexing too.
All this advice goes well for Minmatar, Gallente and Amarr ships, too - just use the ships you are familiar with.