Having recently started Gfx myself, I'll give you the advice people gave me. First, it is not super important for your entire render / stock to be in the picture. The character on the right is squeezed too much, just put in the important part. The background and text is decent for your first attempt, but your 2 characters are just kind of placed on top of it. They do not really blend in anyway.
Just keep on the lookout for tutorials, especially on lighting, blending and flow.