Working from life when possible is always a much, much better way of learning than from ref images.
This may be truer for trees than any other subject.
From all your attempts so far, it's obvious you don't really understand what makes a tree a tree, and additionally you mix fantasy elements such as the big visible twisted roots.
It goes with trees as with characters: you've got to study the anatomy of the actual thing even if your aim is to twist it badly afterwards.
I strongly suggest to go out and sketch
lots of trees, basic and uninteresting as they might look. You will quickly notice that every species of tree has its own typical branch and foliage structure, and you should be able to reproduce those patterns without too much difficulty (branches being easier than leaves though).
The problem with the tutos and examples shown is that these artists have a pre-existing understanding/experience of trees, so their starting steps are actually not starting steps! This is most obvious in st0ven's post (best of them), which doesn't even start with the trunk and branches but obviously has a very solid trunk and branches underlying structure. I'm not that convinced with Perihelion's or the PS tuto, though they are good shading tutos their tree structures are not that great.
Grab that sketchbook already!
