You're making a tree, complete with foliage? But you've only got the branches so far and you plan to add foliage next? Why don't you go ahead and do that then.
I grabbed what you got so far and did an edit for you.
First, "fixing" your tree to look more natural, yet keeping your thick chunky style. Just tried to refine the forms a bit. Then shaded 'er. Altered your dark mauve base color.
This shading style is very uninventive and just plain pragmatic. Easy to do. But a good starting place.
