Ok I've found the answer using google but I forgot to bookmark the reference for you guys but eh.

Basically you have to set properties because DataGridView calls them in order and names the columns with the name of the properties so it's expected that passing a regular list as a data source will produce this result because the only property is Length or something like that (sorry, still very new to C#).

Using the following code for my class Serie made the DataGridView able to display the information I wanted it to display:

Code:
public class Serie
{
    private string  _Name;
    private string  _URL;
    private int     _Quantity;
    private bool    _Follow;
    private int     _QuantityNew;

    public string Name
    {
        get
        {
            return _Name;
        }
        set
        {
            _Name = value;
        }
    }

    public string URL
    {
        get
        {
            return _URL;
        }
        set
        {
            _URL = value;
        }
    }

    public int Quantity
    {
        get
        {
            return _Quantity;
        }
        set
        {
            _Quantity = value;
        }
    }

    public bool Follow
    {
        get
        {
            return _Follow;
        }
        set
        {
            _Follow = value;
        }
    }

    public int QuantityNew
    {
        get
        {
            return _QuantityNew;
        }
        set
        {
            _QuantityNew = value;
        }
    }

// irrelevant code
}