AirMech Arena

Player levels are increased based on experience granted at the end of matches. Typically, you will earn more experience for longer matches, for winning and for having human players involved rather than AI. You will earn experience even when you lose as long as you don't quit out of the match. The winner of a match earns about 50% more base experience than the loser does. Your VIP status affects your experience level as well; gold VIP increases experience earned toward player level by at least 15% and there are boosts available that can increase the experience earned by another 50-300%. Some of the boosts also increase the experience of everyone else in the match and can be stacked by multiple players. Finally, one of the pilots (Eric) will increase player level experience earned at the end of a match by an additional 5%. It is quite possible for a gold VIP player to earn more experience when losing a match than a silver VIP player (or non-VIP player) who wins. 

Focus on unlocking all the other achievements first, other than the three level based achievements and the win X number of matches achievements. At that point, the fastest way to level up is to play co-op 2v2 matches and use the Ultimate Bucky rush approach. 

To unlock "King of the Mountain" will take approximately 85,000 experience. There is no in-game tracker for how much experience you have earned at this time, but on some menus you can see a green line under your pilot's image in the upper right corner indicating how far away from the next level you are. Once you reach level 30, you will then need to win one more match to unlock the achievement.

Ultimate Bucky Rush:
This approach works on every map, but it is faster on smaller maps, so generally try to do this on Dust. At least one of the two players involved will need to purchase the following:

• Ultimate Bucky (in the Units store, requires diamonds to purchase).
• Ultimate Fuel (random drop or often available in the Player store. Currently it cannot be purchased in the normal store). This decreases build time and gives you an additional 100,000 starting credits each match.
• Ultimate Samson (in the Pilots store, requires diamonds to purchase) - Optional, but increases build speed and unit damage so it will decrease the time per match slightly.
• Paladin AirMech (optional, but increases the number of units you can deploy at once from two to four, so decreases the amount of time per match a noticeable amount).

The Ultimate Fuel will need to be equipped on your AirMech before the match starts. On the screen where you pick your pilot, it can be equipped by selecting the bottom left box after you acquire it. At the start of the match, build an Ultimate Bucky and then press  multiple times to fill your build queue. Hold down  to load up your AirMech to maximum capacity and then move toward the enemy base just enough so that you get blue dots beneath your AirMech indicating you can deploy the units you are carrying. Repeatedly press  to drop the units while simultaneously ordering them to attack the enemy fortress. Move back to your fortress and repeat. If you get in the rhythm of pressing  while moving to deploy and the server does not lag, you should be able to deploy 20-24 buckys prior to the countdown expiring. Keep building units and deploying them until you run out of money. You can shave a few seconds off if you go to the enemy fortress and ensure the enemy mechs are not interfering with your units, but they will be unable to stop the attack as a rule so this isn't strictly necessary.

With an idle partner, you can generally win in 55-65 seconds on Dust. With two partners equipped as indicated above and building, you can win in 40-45 seconds. Currently, this results in 180-190 XP per match.

Player levels are increased based on experience granted at the end of matches. Typically, you will earn more experience for longer matches, for winning and for having human players involved rather than AI. You will earn experience even when you lose as long as you don't quit out of the match. The winner of a match earns about 50% more base experience than the loser does. Your VIP status affects your experience level as well: Gold VIP increases experience earned toward player level by at least 15% and there are boosts available that can increase the experience earned by another 50-300%.

Some of the boosts also increase the experience of everyone else in the match and can be stacked by multiple players. Finally, one of the pilots (Eric) will increase player level experience earned at the end of a match by an additional 5%. It is quite possible for a Gold VIP player to earn more experience when losing a match than a Silver VIP player (or non-VIP player) who wins. 

Focus on unlocking all the other achievements first, other than the three level based achievements and the win X number of matches achievements. At that point, the fastest way to level up is to play PvP Custom 1x1 matches and have your opponent quit as soon as the map loads and you gain control of your mech. You will earn 45-50 experience if you use Eric (or Ultimate Eric) as your pilot and have Gold VIP status (35-40 with Silver VIP). You can increase this if you have an XP booster as well. I unlocked an XP booster as the rare consumable that came with my Gold VIP and earned 70-75 experience per match using this method. With loading times, you can do two matches a minute using this method. 

To unlock "King of the Mountain" will take approximately 85,000 experience. There is no in-game tracker for how much experience you have earned at this time, or how far away from the next level you are. Once you reach level 30, you will then need to win one more match to unlock the achievement.