New to Fantasy Baseball a bit over my head in NL only league

[micahsw]

Starting out pretty well, but Belt and Berkman may be holding me back. Thoughts on trades to bring me to the next level would be great as well.
10 team Roto League, NL only.
C: Carlos Ruiz
1B: Lance Berkman
2B: Johnathan Herrera
3B: Casey Blake
SS: Troy Tulowitzky
CI: Jerry Hairston Jr.
MI: Willie Bloomquist
OF: Ryan Braun
OF: Shane Victorino
OF: Jason Heyward
OF: Ben Francisco
Util: John Mayberry Jr.
BN: Brandon Belt
BN: Ryan Doumit

SP: Clayton Kershaw
SP: Cliff Lee
SP: Tim Hudson
RP: Carlos Marmol
RP: Jose Contreas
P: Kyle McClellan
P: Jose Contreas
P: Edinson Volquez
BN: Sean Marshall

It is a pretty deep league so I definitely have some clunkers on my team. Any advice?