Upgrades makes the tank better as you level up. You receive 1 upgrade token every time you level up (2 when you reach level 100) which can be used to invest in the categories below. However, the way these tokens are used varies from player to player, depending on their personal style of playing. You can, however, explore the different combinations and find your own style after practicing, since you are allowed to change the way you have distributed your tokens among skill trees (Token Redistribution) every 7 real time days.
Upgrading the Chassis gives armor to the tank allowing it to take more damage. Each point invested gives the tank 1% extra starting HP in the form of armor. Maxing the Chassis will max out the armor providing an additional 40% HP at the start of a match. The skills in this category give a chance to earn a small amount of HP or armor each turn. It is a great starting skill tree, although some users may find the Track skill tree more effective at low levels. However, if you like to play the game with friends and want to get XP fast, you might want to invest in Chassis; more armor means more damage needed to kill each other, which in turn means more total XP gained at the end of each game!
The skills will stack, meaning there is a chance to recover a total of 10 HP and 10 armor in a single turn if you have all 3 of them! The above skills are rather useful in Juggernaut Mode matches, which tend to last way longer than other matches, giving you the chance to recover a large amount of HP/armor during the match.
the skill points only provide an average of 1hp/armor per turn, many players may wish simply to invest in the +>1 branches and then move on to upgrading gun.
Upgrading the Track will allow tanks to move across steeper terrain, while maxing it out can make tanks get past almost anything on the map, even scale practically vertical hills. The skills in this category increase fuel, allowing you to travel longer distances across the map. Upgrading Track is one of the most often choices for beginner players (even since Level 1), as it prevents the tank from being stuck in the same place, unable to escape the enemy's incoming shots: imagine having all the proper weapons in your arsenal enabling you to take out your enemy, but then getting stuck in a hole or under a steep hill, completely exposed.
It is recommended that you ignore other skill trees before at least 70% of this bar is maxed, otherwise you will be unlikely to be able to utilise the shank, napalm, flame and other short range weapon trees.
Upgrading the Gun increases the chance of a weapon dealing critical hits after firing it, which means that there is a chance that your shot will deal more damage than it normally would. Critical damage starts at 1.5 x the original shot damage and can be increased by going after the skills in this category. Maxed out Gun will give players a 20% chance dealing critical hits, since each individual point of Gun provides a + 0.5% critical hit chance. Gun is not very useful if you don't invest a large amount of tokens into it, as you will rarely get critical hits, though when maxed out it can prove to be a game changer.
completely maxed, it effectivley adds 20% to damage, however this may vary on single blasts such as nuke and pixel, it is thus not as valuable as the +40% max health bonus of chassis, however it will increase your overall xp, it is often debated which is better between the two, however its large xp bonus may be preferable to a mediocre increase in HP.
If all 3 skills are obtained, then every critical hit deals twice the normal damage!
Increasing Luck increases the chance of getting higher tiered weapons in the beginning of the match or in crates. Especially for crates, upgrading Luck increases the amount of loot found in them, while the available skills of this skill tree increase the quality of those items (see below). High Luck has little or no effect at lower levels, as the player is unlikely to own many upgraded weapons that can cause a huge difference in the outcome of the match. Thus, it is recommended that you choose to invest in this skill tree after (almost) maxing out the other 3.
Due to the fact it requires either crates or upgraded weapons to function, this upgrade is not reccomended below level 50, as you wont have many weapons that can recieve upgrades.
Note: The ratio that these skills affect are currently unknown, however, they do increase quantity of drops from crates in most cases.