Get yourself a female clown, when your female is 1k grams start looking for a pewter/superblas het clown male. By the time he is ready your female should be at an ideal weight.

Keep in mind that we can plan all we want but snakes won't always behave as expected. You get snakes that will take longer to get to size, breed, etc. Most important thing is to get snakes you like and have fun.