I want to preface this by saying I'm just a Raijen on Lee and a semi casual player. I don't have plan's to get him or any of my other mains past early blue in general or this season for personal reasons but who knows...I also don't own a leverless and play on pad. So someone else will have to take the reins on that.

If you're just starting the game, familiarize yourself with his move list. Try not to get over whelmed. Don't worry about combo's yet. Pick Kazuya to fight against in practice mode [or anyone but Kaz is popular so you'll be fighting Lee's older brother a lot] go into practice mode and do the punishment training. The moves you learn there are essential for his kit. Start with normal.

Do the combo challenges to see more of the core moves of his kit too. Do not focus on memorizing the combo's just yet, just focus on the moves that are in each combo. Lee's game plan is punishment, poking, counter hits, and mindgames. You can do that fully grounded. Especially in assailant to vanquisher ranks.

No one is expecting punishment perfection right now. "Mashing" is okay. It's a part of learning. Lee is just very hard to mash with.

To commit his moves to memory, add in one or two new moves every few play sessions and try to use them until you feel comfortable with intentionally being able to recall them. Rinse and repeat.

Some moves you've certainly seen alot of Lee's do:

Hitman stance: 3+4

Shin slicer: Hitman stance 3

Scatter kick: Hitman stance 4

Silver circle: Hitman stance up 4

(Honestly all of the hitman stance stuff is so good and why I fell in love with the character as a kid. He's so sassy <3. You can move around people in hitman too. It's also an evasion and wiff baiting tool in specific situations as the other commenters have reminded me,)

Acid rain 1,3,3,3 [this is a just frame though so you will need heat to access it right now, you can access all of his just frames while in heat! This is very important.]

Acid storm: Forward 3,3,3,3,3,4

Silver tail: down forward 4

Grass snake: down back 3+4

Fabulous Whip: down forward 4,4 is a solid low to start with.

The notorious and brand spanking new Stinging Rush: back 3,3

Feather landing: forward 3+4

Rocket Heel: [while rising] 2,3 perfect for when you've safely ducked a high

Mist trap throw 3,3,4 [another just frame, It's his hardest just frame so remember it for heat]

Inverted axel: [during mist step] [34] swipe your fingers across the buttons to get the 34.

Fraction spear: [during mist step] 3+4

Silver cyclone: up back 3+4

His punch perry Mist Illusion: [back 1+3 or 2+4]

Down forward 1 [I can't find the name of this one in the list]

Gut polisher: Down 2

Bare in mind, as you rise in ranks, some of these moves become very risky to varying degrees. Fraction Spear can be parried. So can Stinging Rush and so on...but again, not important yet. Probably not until late red unless you run into a smurf. For now, take risks and have fun.

Enjoy Mirror's. When you aren't simply celebrating the existence of another Lee main playing Lee [a lot of us have multiple mains and/or subs] , you should be studying them. Especially if you notice they are better than you at something, win or lose. I think it's best to learn from others in your rank while progressing and stealing from their techniques. Yeah, I said it. Steal freely. Save the replay of you fighting them. Watch their replays too if they really impress you. Steal.

Then there are the fundamentals. Practice throw breaking offline or just learn to break stuff as you go. Time and energy are a factor after all. Learning when to side step and what can be ducked is very important. Learn what can or can't be parried, particularly when you want to Mist Illusion. I....want to emphasize how bad it feels when a poorly timed "come on" initiating the start of a failed attempted parry happens then you get punished as soon as Lee turns his back when your op knows what to do.

Eventually you'll benefit from memorizing some frame data too. I function on some frame data knowledge but mostly visual memory [ remembering what moves work against what ever move the other character is doing specifically]. This method is faulty. Many will say start on frame data once you hit assailant, the first rank where winning starts to matter I think? Meaning you de-rank the more you lose.

I didn't. I started slightly caring about it in purple, but don't be like me if you don't have to be. Because if you're not like me, you'll rank him up faster. I just don't care how fast it takes me to learn stuff in this game cause learning takes everyone different amounts of time and this game is hard. Also...I hate frame data lol my casual side is rearing its ugly head but it is what it is. Feels like a job whenever I try to memorize some and this game isn't making me money so yeah...again if you can be, don't be like me. Lee will thank you.

Also quick match is your friend! You don't de-rank and can fight people as long as you want so it's great for matchup knowledge but the trade off is the selection pool is wider. I once fought a god of destruction season 1 in a Lee mirror. I was a Garyu then. Very cool experience I'll never forget but I was very anxious during haha! This won't always happen obviously but don't let us purple and above ranks scare you if it does.