It takes 420,000 to get to lvl 50, Getting to lvl to 13 gives u Grizzled... Just play Ground Control so when u get a capture u get between 1,000-2,500. When u get to level 7 u unlock BC(Battle Commander) which gives u more points..
Getting kill streaks give u bonus.. Kill someone with a kill streak gives you big bonus.. Kill someone who has a 5 star(which is 15) kill streak gives you 10,000 plus what ever other points for the regualer kill..
Depending on how good you are, and how the servers are it can take around 15-20hrs to get to lvl 50..
It takes 1,200,000 to get to 75...