|Melee||+5 more Energy per lvl|
|Defense||+5 more Health per lvl|
|Sword, Gun, and Blox Fruit||Higher Damage per lvl (0.5-1 per lvl)
You can also get 1 stat point for a certain category for every 3 mastery points you have on the category's weapon. (If you have 3 mastery on Flame, then on stats it would say, the amount of stat points you have plus 1 point. )
You are strongly advised to max melee, defense, and one other damage stat to the maximum level. Otherwise, you will have a disadvantage in PvP, since you have less health, damage, and energy.
If your character is built in a way it has max health and energy along with max sword stats it is called a sword main, when the same is done with max fruit stats instead of sword it is called a fruit main. There are a handful of people who build their characters so that the points are distributed either equally or to all stats theses players are dubbed hybrids' as they have points distributed to all stats. Hybrids, while being versatile, have a huge disadvantage in PvP, PvE, and raids, but have a new world to explore as they are not bound to one single stat.
People who have max stats in devil fruit have an advantage in all fields if they have a good fruit, and the ability to use it well. There are many players who main fruit, as it makes it easier for the player to swim through all the tough challenges with ease. It is recommended to go fruit main for raids since they have more moves to deal with large amounts of enemies without having to wait on cooldowns. Players might face difficulty as they cannot deal much damage or are in limbo if the fruit they are using is in cooldown, these player are found basically in all servers. Unlike the other stat distributions, fruit mains don't necessarily require a good support gun/sword and are thus easier to use if one doesn't prefer to combo. (2099 melee , defense and fruit)
People who have max stats in sword hold a tremendous advantage in PvP if they are a good player who can make spontaneous decisions and are agile. It is common to find people who are a sword main in late game as it considered to have a disadvantage in raids and PvE as there isn't much they can do. It is extremely common for sword main's to use a logia as they can have mobility as their moves are on cooldown. If these characters have the right weapon in their hands they can rival fruit mains. Most people with a bounty higher than 5.5 mil are sword mains. (This was proven via a server 71/100 people were sword users). Swordsmen, like gun mains however not as prominently, need a good support fruit/gun in order to land versatile combos. (2099 melee, defense and sword)
People who have max stats in gun and hold a great advantage in PvE (specifically bosses) and, if used correctly, PvP. With good timing skills and aim guns can be very formidable in PvP. It is very rare to find people that use guns for PvP. Most gun users incorporate a mix of other forms of fighting to compensate with the difficulty of dodging enemies. Guns in raids are not too useful since they do deal hefty damage but have limited moves and AoE isn't too large. Gun mains, similar to swordsmen, need to have a good support, either fruit or sword, to compensate for the hard to land moves. Good fruits for gun mains would be stun fruits that allow the user to land moves in combos.(2099 melee, defense and gun)
People with a diversity among the stats they mostly don't have a maxed out stats and have stats in all fields, few have max health and energy, but distributed the rest evenly. These people have disadvantage in both raids and PvP ,but have a new world to explore as they aren't bound to a specific weapon or asset. (1400 defense, 1300 fruit and gun or sword and gun, the rest is melee)
As of Update 16, the max amount of points you can put into each stat is 2099 (1 free bonus stat so you can only put 2099)
Stat refund codes : Sub2UncleKizaru, SUB2GAMERROBOT_RESET1, THIRDSEA, 1MLIKES_RESET
Mastery will unlock different moves of your devil fruit. For example, most devil fruits have 5 moves. The first move of every moveset costs 1 mastery (other than some exceptions which have their first 2 moves unlocked). The second costs around 25-50 while the next costs 50-100 and so on. Currently, the Death Step fighting style has the highest needed mastery.
Mastery can be gained by defeating NPCs. Bosses usually give alot more mastery than normal NPCs