About the world of Alk. It is a fantasy world that has a system, monsters dropping loot, and instead of a skill tree a system contained shop. The shop skill books, recipes, and spell books people can learn from and use along with the ways described below can be bought with gold. These can be opened up to buy a single time so people won't usually be willing to hand to others by performing tasks related to the skill, leveling a previous skill, or accomplishing a feat related to the skill. I have tried to think of ways to balance everything but I am human so I am biased towards the mc's class. There really aren't any limitations to how far you can go in this world so some characters may just be off the power scale in this one. 

Classes I have thought to include

Magic Cook-Really any type of making food or drink, using mana infusion into ingredients, monster parts, and just plain old regular ingredients to make a great temporary boost or give a specific power. Anyone who consumes these will gain their effect but they usually last very long as the magic acts as a kind of preservative. Recipes can be created by a cook who researched or tweaked a previous recipe or found off monster drops. Limitation is that everything is temporary and will eventually end, they need ingredients to make the edible, and everything must be premade along with the fact that they are not first and foremost fighters. 

Mage-Those magic users who use spells to attack, defend, summon, sing magic songs, or buff/debuff others and themselves. They can also either create spells themselves through a variety of ways including vocal and hand drawn in the air with magic or get a spell scroll off a monster. Their weakness though is that they are physically weak because the mana generation inside of them takes a lot of energy from the rest of the body giving them that classic wizard feel and that they can just up and run out of mana to cast spells.

Warrior-Classic weapons users(not including bows) and martial artists who use their body and skills to fight. They also can connect to their aura to wield enhanced powers giving them greater strength, defense, or versatility. These skills can either be developed by the user or found off monster drops. Their limitations are that they usually have a shorter range than other classes, require certain weapons unless using fists to activate many skills, and that if their aura runs out then instead of strengthening they will gradually weaken until they collapse due to the heavy strain of using their aura.

Magic Craftsman-Enchanters, inventors, blacksmiths, whatever makes something and infuses the material with mana or use monster materials to create long lasting unconsumable products. Their equipment and tool designs can be created by a craftsman who researched or tweaked a previous design or found off monster drops. Their limitation is that the effects of the longer lasting equipment is a lot less than temporary consumables and they need materials to create their stuff along with not being fighters.

Rogue-They are those sneaky types or those who follow the fight smarter not harder mindset(bow users too). They are much like warriors except they focus on using tools and stealth skills to make ambushes and clever hit and run fights or kills. They make great scouts as they can focus on their surroundings more since as stealth users themselves they have a better eye to find hidden enemies and traps. Their limitation is that they need to acquire tools to use, although faster because of lighter gear weaker in frontal combat than warriors, and that they are easy to keep sight of once noticed because shockingly enough, people are more likely to notice and look at the person who just appeared as if out of nowhere.

Clerics-Yes, the healers, or more specifically the followers of gods. Their powers vary based upon their god but because their gods usually like their followers surviving, most clerics have healing spells in their arsenal. They are much like mages in that their devotion takes a lot out of them but paladins are those who choose to be champions of the gods and instead for weaker godly powers they can keep their strength. They may keep their strength but they are still weaker than pure warriors. Many gods, consider themselves as great beings of holy righteousness so they also have many with godly buffs against the dark and undead powers. The gods themselves can add their godly skills to their cleric's system shop which their followers can purchase not with the usual gold but faith points that as beings that can interact with the system can have the system grant automatically for following their god's doctrines and performing feats.

More classes could be added later on whenever I feel like it but I'll start with this for at least the first 10 chapters.