Rescue: Bloody easy to use. Their more useful cards tend to be quite expensive tho', and you'll need to play them in Mono, meaning you need 8 good cards of them.
You may have better luck just going with Montana.
Sentinel: Not really great or bad at anything, imo. With Lehane gone you won't have (m)any Elo banning issues either. Also quite cheap, not counting Melvin and Coby.
FPC: Always safe from ELO bans. High power and good damage, making them very straight forward and fairly easy to use. Unfortunately higher powered cards tend to be pretty expensive with the exception of Futoshi LD. Having said that, with Ralph, Unagi, Sayura and Yu Mei you have a ridiculously cheap half-deck that can still pack a punch, especially for a beginner.