You gotta play a lot. I climbed to legend by playing 122 games with 73 wins and 48 losses. And as you can tell, it took quite some time.
Be patient, don't rush it. I find it hard to get legend every single season, but as i practiced more, i saw myself improving and getting to legend more consistently.
You should try to tech in some cards like acidic swamp ooze if you're facing many hunters and overload shamans. Anticipate their moves, play around certain cards. Try to set up for lethal whenever you can, know when to play certain cards and when not to. There are hundreds of tips that you will learn to pick up as you play more. It's a learning process , so you got to keep a clear mind and not tilt so much.
Just keep playing and you gotta think while you play. I know it sounds stupid, but most people play on auto pilot mode after a few games. Get good with one deck, then just focus on getting good with that deck and don't give up, that's how you get to legend in my opinion.
Oh, and ignore those people who keep saying that being lucky is the only way you can win games. Luck can win you a few games, but it doesn't make you a better player. This game still takes skill and effort, watch how professional streamers play their games, and you'll realize that luck can only take you so far.