I am a genji main, and I have played genji for over 200 hours, and I am in diamond on my main account, and my tips for genji are: aim doesn’t matter as much as much as other heroes do, you just need good game sense, learn your combos, avoid fighting mei, briggitte, and mccree in close range so you wont get stunned or frozen. Genji’s biggest enemy is crowd control, or any hero that can effect your movement. Always save your dash for disengaging if you dont think you can finish someone off quickly. Use tanks like dva roadhog and rein to charge your ult quickly, and always melee.
When to engage as genji: usually engage when your entire team is pushing, or when you see ann enemy healer or dps heroes like hanzo, soldier, bastion, widow, or junkrat that is somewhat away from the enemy team, dash to them, finish them off, then dash away to safety
How to use genji’s ult: when you have your ult, either combo it with nano, grav, shadder, or tell ur mercy to pocket you. But before you ult, kill the enemy zen or lucio, or tell your team to put pressure on the enemy team to force out trans or sound barrier, then you will be able to ult safely. When you can ult, dash into the crowd of people, turn around then ult, and dash through the crowd of people again to deal 100 damage(you’ll have to do all of this really quick, or you won’t be able to pull off a good blade), after that, turn around again, and slash, and it should kill someone that is not a tank. After you’ve killed the first person, dash to someone else, slash, then do that again and again until your ult goes on cooldown.