TimedBuff.cs

public abstract class ScriptableBuff : ScriptableObject
{

    /**
     * Time duration of the buff in seconds.
     */
    public float Duration;

    /**
     * Duration is increased each time the buff is applied.
     */
    public bool IsDurationStacked;

    /**
     * Effect value is increased each time the buff is applied.
     */
    public bool IsEffectStacked;
    
    // Time between each tick 
    public float TickTime;

    public abstract TimedBuff InitializeBuff(GameObject obj);

}

public abstract class TimedBuff
{
    protected float Duration;
    protected float TickTime; // time until ApplyTickEffect() is called
    protected int EffectStacks;
    public ScriptableBuff Buff { get; }
    protected readonly GameObject Obj;
    public bool IsFinished;

    public TimedBuff(ScriptableBuff buff, GameObject obj)
    {
        Buff = buff;
        Obj = obj;
    }

    public void Tick(float delta)
    {
        Duration -= delta;
        if (Duration <= 0)
        {
            End();
            IsFinished = true;
        }
        TickTime -= delta;
        if (TickTime <= 0) {
            ApplyTickEffect();
            TickTime = Buff.TickTime;
        }
    }

    /**
     * Activates buff or extends duration if ScriptableBuff has IsDurationStacked or IsEffectStacked set to true.
     */
    public void Activate()
    {
        if (Buff.IsEffectStacked || Duration <= 0)
        {
            ApplyEffect();
            EffectStacks++;
        }
        
        if (Buff.IsDurationStacked || Duration <= 0)
        {
            Duration += Buff.Duration;
        }
        TickTime = Buff.TickTime;
    }
    protected abstract void ApplyEffect();
    
    // Apply some 'tick' effect such as damage (bleed, poision, etc)
    protected abstract void ApplyTickEffect();
    public abstract void End();
}