Well this cant be actually answered right because it depends on you, but i recommend to you to play maps wth AR8 and when you see you can FC them jump to AR9, why? well if you really want to play DT like a basic mod then you would like to get used to the speed, and then you will have to get used to AR10+ cause you will have to train reading
Also check out BPM i dont recommend more than 230 but you can figure that out by yourself