Here is killstreak xp multiplier
Here is a few more ways to earn xp
Also, they have stated they will eventually try to make leveling up a little bit easier as stated here, [quote=“JollyajaX, post:7, topic:70802, full:true”]
I agree that Ground Wars leveling is overly slow. We’ll aim to fix this in a future patch.
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Like said above, welcome to the forums! Be sure to use the search feature 
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