Celvincen, let’s speak of a serious truth: Do you know all these ground-shaking, industry talented artists? They’re not talented. They most likely won’t appreciate being called “talented”, since the general concept of talent means an effortless, almost magical gift. It was anything but effortless for them.
You can make it, that’s certain. But there is a price to be paid. Yes, it may be literal, you can take classes if you can afford it; or even buy cheaper material, nowadays there are some nice tutorials and stand alone lessons floating on Gumroad and the like. It can be figurativea lot of time and effort and some blood tears.
The best place for you would be the sketchbook section of a big forum. Some place busy and active, where multiple artists can drop their critiques and suggestions. Peer review is important, the multiple points of view can only add. You can send me some PMs, the problem is that I’m very far from active. Something along the lines of a couple of apparitions per year, and that’s everywhere on the internet. I’m one of these who step out of the cave once in a while, hiss at the Sun and scramble back to the rock they hide under, you know.
The best advice I can give you now is to intercalate studies with original works. By studies I don’t even mean super detailed, perfect copies. They can be speedpaintings. You’ll need to figure what works for you. Pick one, two subjects at time only, e.g.: values (shades only) and… feet. And go for it. ~4 studies, then an original applying what you’ve learned. That way you’ll improve and produce originals for your portfolio at the same time. 
Trace a plan. Since you’re having trouble getting into the industry and already have a graduation, why not work in this field while you study 2D? Once ready, make the switch. I can’t tell if it’ll be fast or not. I’ve seen artists become cream of the crop in a year. Others, like me, are painfully slow learners. But that’s a plan anyway, concrete and feasible.
Regarding portfolio and what you can study: Work on your volumes, start from the basics, shapes and plane changes. Anatomy is important, vital if you want to work with characters. Environments certainly don’t hurt, and you’ll need to study perspective for both. Colors are a plus. I’m a bit suspicious to talk about colors, since it’s the main hook of my work, but I can say that the use of colors can enthral people, and you want to hook your potential boss with some aspect of your work. Light is deeply linked to colors, so… Break each one of these in smaller pieces, focus on one each time. Get comfortable enough with each element, then move on. You’ll see you’ll start to apply what you learned without giving it a second thought. It’s like a trained muscle.
That’s it. I’m afraid I’ve digressed a little. Sorry!