Worms Rumble

Pay attention to the "Laboratory" mode. Sometimes there is an “infinite weapon” mode or only one available weapon (for example, a bat, a plasma gun), which helps to gain a level very quickly on some types of weapons

Some personal observations to help you understand this ridiculous experience system. I immediately advise you to pay attention to the turret launcher and rocket shield; these weapons are the most difficult to deal damage with and they are quite rare. It's easier to level up in the last squad mode. At the very beginning, you can open a bunch of chests. Green chests usually drop small arms and bazookas, blue chests contain weapons with special shells, and red and purple chests have a high chance of getting a hammerhead shark.
The maximum experience for using a weapon (in fact, you just need to hold it in your hands) can be 500xp - this is two minutes of time in the last squad mode. In the same mode, you can more easily gain experience for weapon damage: 1 damage = 1 xp, maximum xp per damage = 200. For destruction with a weapon, 50 xp is given for each worm, the limit is still unknown. Damage to knocked out worms does not count. Also, experience for carrying is sometimes not credited, so double-clicking on the triangle to rotate the weapon often helps.