The biggest advice I could give for this achievement is to not get obsessed with scoring 1 million without a death. Make it a goal to reach a high score of 3 million and if you haven’t got all the achievements in the game by then, I’d be surprised. Even if you didn’t then you’d certainly be close. Quitting out when you die and starting again is preventing you getting better at the game.
I’ve made a video where I get all 12 achievements in one run. Watching a video isn’t going to make you suddenly able to do it but it helps to see the strategies for the different waves of enemies.
I personally go clockwise (unless there’s something making me temporarily change direction) but if it feels more natural for you to go anti-clockwise then do so. It’s 50/50 for preference amongst the top players. Also make sure to practice wiggling the right analogue stick when firing to spread your fire. Good luck: