Instead of setting all the numbers in Class, your actor gains stats according to your formulas.
The stat you want to be increased by formula on level up, write e.g.:
<MHP: 50 + (@level/10).floor> – Actor will get 50 HP + extra HP from 10th level.
<MMP: 10 + @level> – Actor will get 10 + number of his level Max MP.
<ATK: @level> – Actor will get his level number of ATK.
<DEF: 3 + @level> – Actor will get his level number + 3 of DEF.
<MAT: 7> – Actor will get plain 7 MAT each level.
<MDF: 5> – Same as above, just 5.
<AGI: 5 + rand(3)> – Actor will get 5 + 0/1/2 AGI per level.
<LUK: 1> – Actor will get flat 1 LUK per level.
In actors note tag.