Experience is gained by doing 1 thing only, and that is getting kills. There is currently no other way what so ever, to gain XP. Also, all game modes give the same experience per kill.

Remember this...

1 kill = 5 experience
1 kill + Premium = 10 experience

Considering the only way to gain XP is by getting kills, you want to go to the gamemode or map that you can get the most kills in the shortest amount of time. I personally prefer versus mode, since it has smaller maps. So there is typically a lot more killing in versus than in any other gamemode. Another thing is to stay in servers that have more people. More people = more kills... which than makes you more XP.

Just to simplify what I just stated...

Play in high population, versus servers.

A high percentage of blockades top players, typically spend most of their in-game time in versus servers. So for newer players, it will make it quite difficult to gain kills. I have 2 solutions to fix that...

1. Buy double armor ($1.98 total for helmet and vest.) This will allow you to survive a little bit longer against people using most of th gun in the game. Which will allow you to gain a few more kills per death.

2. Try playing a different game mode like battle. Battle mode usually has less experienced players who you can practice your aim/reaction time on.

Q. Why don't I just play battle?

A. Most battle maps are bigger than most versus maps. So it will take you longer to get kills.