Systems don't even need math. Or at least nobody needs to know how it calculates.

For example some systems don't use numbers, they use something else like chess piece ranks instead.

The only thing that matters is if you want to use math and complicated formulas.

Consistency is far more important than complexity. For example rather than having health be constitution plus half of vitality plus 0.3% of willpower multiplied by level just make it its own stat. Then just keep a character sheet and make a note when things change

Exactly. Keep it simple.

The lightest litrpg I ever wrote (well, half-wrote, it's still at 60k words for almost two years now) is that simple: 1 stat - level - and 1 power per level. Level increases your power's range/amount or decrease your cooldowns by 1/6th, multiplicative (that's what the Xy key on my laptop calculator is for).

And that's it. There's plenty to create a story from, since it's the interaction between powers that you have that makes the plot advance rather than math.






Levelling stats up, is akin to body modification as people body can change

Simple formula

Every level
Gain HP current( base 10 hp+strength (1/3)+ endurance)
Gain mana (base 20mp +intelligence + willpower(1/2)

Every level gain +3 free skill points to allocate

Strength
Endurance
Dexterity
Agility
Intelligence
Perception
Willpower


HP  base 100 + ( endurance+strength*
Mana intelligence+willpower x2

Stats are gained through training

Every 20 points grants a feat of power ( a special skill)



Damage
Small mobs
 0.5% to 5%
 Critical
5% to 15%

Medium grunts
 6.25- 20 %
 Critical
10%-30%

Higher levels and bosses
15%- 45%
Critical
45% to 70%