I have been climbing with Sym until Diamond 2 but I feel like I'm a little stuck now, is there anything specific I need to do to climb more towards GM and beyond?
I can't really give specific advice because it's different from person to person. When i want to learn a character I normally just watch high rank players play them then watch back my own gameplay and try and work out the differences in gameplay and match my gameplay to theirs as a good starting point.