Im currently rank 60, on prestige 2. I find the best way to rank up is simply use specialist kill streak with hardline on, (gets you tons of exp when one is earned) and play the game mode kill confirmed, also if you havent yet registered to ELite, register as you will get 2 hours double exp for free.
As of for guns/perks i would really look into that yourself on what guns/perks you seem to like and do well with, i love the type 95 and currently have a 2.13 KD

GingAARGH

USE specilest and also use diffrent wepons i am leveal 70 no prestige but a good way to rank up is to use diffrent wepons so then you will complete more challenges and then get more XP also its importent to search around for a game that your good at like i play kill confiremd and ground war but just search around for a game that soots you and B.O.BS your uncle
hope i helped.
P.S also i play with my freinds cuz they talk and then i dont get to mad if i die cuz its importent that you dont get mad cuz i found the more mad you get the more times you die

use the specalist strike package, people under estimate it, it is actually good

Play domination with a full team,

If you don't like domination, play kill confirmed.

Also if you know people that have double xp codes just lying around, those always help out too.