So, I'm gunna hack together a response from a few different places. I sort of have a cookie-cutter document I carve from now and again when people ask these general questions. If all of this doesn't align perfectly, my apologies! I'm going to tailor some stuff in the response but it might be a little more of an overview.
Here goes:
**Some of the personal story.. **
I had to go through several phases of life in order to get to my current position. I attended Pratt Institute in New York to get a bachelors in art, then however found that the type of art I did wasn't in demand on the East Coast. I left my home and family to move to Los Angeles to attend Art Center College of Design for a brief period while I learned specifically about entertainment art. These two colleges alone cost a fair amount of money.
My early days in Los Angeles were filled with uncertainty as I wasn't sure how to achieve what I wanted to. I worked as a prop-maker in film for a long time, for low wages, desiring to get deeper into the movie industry. Only later was I clued into the world of video games as being ripe for concept artist opportunities.
Even then, I put a significant amount of work, on my own time, of creating a robust portfolio. I worked many low-paying freelance jobs before accumulating enough good work that would impress a studio. Once I was in a good place, I was able to take on freelance work for Riot and eventually prove my worth as an in-house hire.
All in all, a lot of time, money and emotional struggle was spent, but it was unquestionably worth it. Going through what I’ve gone through has given me a unique perspective and helps me not only technically, but also allows me to work efficiently with other artists, communicate, collaborate, and be able to function as a productive part of a team I love being a member of.
In terms of specific instruction on direction and craft..
First, figure out exactly what you want to do.
If concept art is indeed where you’d like to focus then the first and foremost thing to do is to draw. Draw a lot. Have an unquestionable understanding of form, color and other artistic principles. Be able to recreate life from your head and then be able to build on that with your own ideas. After you can represent what you see in life, create your own worlds. Show how many ideas you can come up with. Be comfortable with coming up with hundreds of ideas and narrowing down that lot to a small number of options. Be able to technically take those sketches, drawings, etc, to a level of high illustrative polish.
Knowing what 3D artists need from a concept artist is key in that we create work which they use to create a final model from. Working inside constraints of the entire pipeline is necessary. Becoming familiar with the duties of the people that will eventually surround you is really valuable. Everything you design has to be made. That thing being made has to work. It has to move. There are real limitations. Knowing when you're designing armor how to avoid shoulder pads clipping into a dude's head is a good thing to know.
In terms of education..
Various individuals on the Concept team have varying levels of education or credentials. Traditional education is not a requirement, but it tends to be the way most artists achieve their general toolbox of skills. That said, there is no specific academic credential needed to hold a position as a concept artist at Riot.
What is important is learning the aforementioned skills to pay the inevitable bills. However you get that is up to you. Indeed, ala carte classes are really valuable, and extremely appealing given that most studios don't require education credentials. CDA, Red Engine, Schoolism, etc are all totally viable. I'd go as far as recommending CDA because I went there while I was freelancing. Very worth it. Same can be said for artists teaching their craft on Patreon or Gumroad. Those are amazing resources for aspiring artists and they incentivize artists to teach.
Live figure drawing at any college/workshop that offers should also be on the list of resources. A mix of in-person education, online tutorials, art communities and a host of other non-traditional education methods are at your finger tips. Definitely dig into those.
Some info on "soft skills"..
Meet people, create relationships and generally be cool. There's a host of game development communities. Talk to people. Get to know others in different disciplines. Never be shy about asking questions or turning down an opportunity to make a friend. It might sound a little cynical, but relationships foster new careers. If you're a known quantity to someone, there's a higher likelihood of getting hired somewhere.
I think as long as you are developing personal relationships with people you're doing something right. You want to make sure you're comfortable with people and want to engage personally. I believe relationships, friends, and eventual colleagues are invaluable. At the end of the day you are going to meet these people around town, look at their work, and eventually possibly work with them. It's important to be regarded as someone who is positive and engaging. I very much like interacting with people so I feel that helps me.
Some people have gotten in "easier" or maybe in a way more "traditional", but I think everyone's story is unique and inspiring regardless. Everyone who enteres into the field is tremendously talented. Where they end up is a testament to how hard they've worked and how intently they've kept focus on thier dream.
I would very much encourage artists to meet as many people as possible. Attend workshops and events. Draw with friends and generally get to know people to learn from them and to seek friendship. It's discouraging to work for the dream in isolation. Knowing people involved in the industry is great for learning but it's wonderful for genuine connections. People like to help friends and they like to help out people with potential, artistically and personally.
Hopefully that helps and makes sense. Sorry if there were some incongruities in there. Sorta kinda using a template here.