You got a 12m2 now, and you should definitely get a 9 to complete, NOT an 8m2.
In the future, when you get better and ride in the winds you got there, you will need a 7m2 also, and if you get into waveriding, a 5m2.
Then you got the smallest simple quiver that covers just fine, if average weight
The 9-6 gap has been tried by many, but they have ALL been so dissapointed, and had to sell one or two kites later and buy new ones, to get the sizes to fit - simply too big a gap
When above 10m2 the gap size almost dont matter at all - bigger gap is just fine