Alright, alright no more bullying...
Start with Team Death Matchs(T.D. or T.D.M.) because you can get yourself used to the controls, and respawn alot, so you can train alot.
After you're pro with TDM you can try Search & Destroy(SD).
After that you can try Elimination Mode(EM) and Ghost Mode(GM)
And if you just want some fun, go on, play some Mutant Mode(MM) matches.