I've never used gouache, or acrylics, as they dry too quickly for me. I am a hopeless painter and need time to work the paint and wipe off when necessary. Acrylics, I find, don't allow me to mix subtle colours, and I have not been able to use glazes to overpaint and modify earlier work. Oils let me work slowly and let me modify what I've done. I'd prefer to work quickly , but I haven't got the skill to do that. Van Gogh used oils and worked quickly (but carefully and delicately) but he didn't overpaint - he used hatching techniques to do optical mixing.
I like your painting. Reminiscent of Hockney and (early) Lucian Freud in its subject.
Keep up the good work.
How long have you been painting?