Many of you are veterans in this and probably came across many stories with the system, even written one.
Do you have any tips regarding it, how it should be potrayed, the ExP system or the achievement part
Not an expert, here's my 2 cents.
Systems is a double edged sword. Use it well, and it moves the plot, use it badly, and the story goes bad.
Systems are like deus ex machina, but stretched out. MC encounters a problem, MC engage in conflictd, MC solves problem and grows as a person.
If the system resolves the conflict, or hijack characters motivations, I think that'd do bad for the story.
If you were thinking more about a system with stats, more close to RPG, you know, Atk, Def, HP, etc. Or just the ones from Solo Leveling, limit the stats to only what's important for the story.
For example, if no one needs to know about some obscure stats like "avoidant" or "Magic Def", just don't include them. Too many numbers isn't gonna make the readers more engaged, and I think it's a pain in the but to write and keep track off.
Next, decide whether you want the system to be a character or just a tool. Character means personifying it, give it a name, give it dialogues, give it a personality, may be even a body. However treat it then as you would any other characters: know their purpose, and don't just make them some extra some dude who does nothing for the plot.
If it is a tool, then try to not focus on it too much. Like I said, no one likes to crunch numbers when reading unless they are REALLY REALLY invested in your story.
In that case, know that your system will serve as convenient explanation generator.
How does the MC has this much money? System.
How could the MC have this many powers?
System.
Just try not to overly rely on Systems to move the plot (I'd recommend not to do it at all), or else the story will be made meaningless as would one that's filled with deus ex machina.
As for ExP, don't let it dissolve the conflict, but rather serve as means for the character to grow.
MC fights big boss, defeats big boss, gain exp, level up: good.
MC fights big boss, somehow gets exp, reversing the tide and defeats big boss when he otherwise wouldn't be able to: bad.
For achievement systems, I'm not sure what you are referring to, and haven't really read much of this kind. I'm assuming achievements will grant characters rewards out of thin air or something, so just, again, try not to let it dissolve conflicts, and try not to let it hijack characters motivations.
Open to discussion.
This just proves my point. That can be achieved without any system, and the story wouldn't change a bit I don't know about others, but I find it more engaging, valid, and simply better if a character grows stronger because of their own action instead of because the virtual number goes high
This