I'm quite of a novice in drawing, since I've recently started drawing again after a few years break. I've immediately revealed two of my old problems: troubles with facial expressions and gestures of my characters, and the staticity of positions. I was recommended to use manga tutorials to improve the anatomy (such as http://drawdoo.com/topic/anime-manga/ with its variety of doodles and Drawmanga, with their attention to certain details). I did learn to draw characters in objects in different positions from manga tutorials, which was a progress. Interestingly, due to manga training I've even made progress in prospective, although I was afraid that wouldn't be the case.
What is troubling me now is that, despite the progress, my drawings still seem quite static to me. Plus I started to tend to minimalistic, conceptual-only art. I'd like to get an advice, what kind of training will be the best next step for me?
I fully understand your struggles. My own art skills developed with drawing manga, and it wasn't until years down the line that I got stuck in areas similar to your own.
What I found is that manga makes for a very poor base to work and learn from. At its core, manga is a cartoon, a stylized representation of what we see in real life. When you use it as your guide to learn how to draw, you do not learn to understand correct anatomy and end up struggling because your brain can't 'connect the dots', so to speak. You're basically trying to fly when you haven't learned to walk yet!
The best way to remedy this is to discard manga tutorials and focus on realism - gesture studies and using real people as models to study from are the way to go. This probably sounds like something you don't want to do because I'm guessing you really enjoy the manga style, but fear not, you don't have to give up manga all the way. :) The idea behind this is to make your brain see real life and give you the ability to put it down on paper first in a way that makes you understand how things go together. When you know how to do this, you will be much more capable to apply this knowledge to your manga drawings and give them the life and dynamic feel that you're yearning for now.
Knowing how a body is put together, how the joints work in movement and what gives faces their special expression from real life studies is a base that you can stylize later. It's like putting down the foundation of a house and building the walls, then painting the walls in the color you like to make it what you want it to be. You can put motifs with wallpaper and whatever you like on there, hang up pictures, put up shelves, but you'll always have a sturdy wall making that possible.
I hope this wasn't too confusing! If you want to get started with gestures but don't know how, I recommend these articles:
My suggestion is to just keep practicing. Thru time and practice, your hand will get used to those types of movement when drawing facial expressions and you will get better with it. Here's also another tutorial that might help you http://www.painterartist.com/en/pages/draw-manga/expressions/ for the facial expression problems you have ;)