Render 2D text for screen

Hello! I am making a small font engine for draw statistics on screen. My example:

My system is worked so: 

1.  I create dynamic vertex buffer with size float3 (position) x float2 (uv coordinates) x 1000
2.  Start game loop
3.  For every frame I map vertex buffer (font engine)
4.  I update necessary vertex (fps etc)
5.  Unmap vertex buffer (font engine)
6.  Draw vertex buffer (font engine) (1 draw call)

I am kind of a beginner (many optimization concepts are not familiar to me), so I wanted to know:

1. Is this way of drawing text effective? After all, the constant display of memory …