How to add buttons dynamically to my form?

It doesn't work because the list is empty. Try this:

private void button1_Click(object sender, EventArgs e)
{
    List<Button> buttons = new List<Button>();
    for (int i = 0; i < 10; i++)
    {
        Button newButton = new Button();
        buttons.Add(newButton);
        this.Controls.Add(newButton);   
    }
}

You aren't creating any buttons, you just have an empty list.

You can forget the list and just create the buttons in the loop.

private void button1_Click(object sender, EventArgs e) 
{     
     int top = 50;
     int left = 100;

     for (int i = 0; i < 10; i++)     
     {         
          Button button = new Button();   
          button.Left = left;
          button.Top = top;
          this.Controls.Add(button);      
          top += button.Height + 2;
     }
} 

You could do something like this:

Point newLoc = new Point(5,5); // Set whatever you want for initial location
for(int i=0; i < 10; ++i)
{
    Button b = new Button();
    b.Size = new Size(10, 50);
    b.Location = newLoc;
    newLoc.Offset(0, b.Height + 5);
    Controls.Add(b);
}

If you want them to layout in any sort of reasonable fashion it would be better to add them to one of the layout panels (i.e. FlowLayoutPanel) or to align them yourself.