There's a hole in my bucket..bucket size transplant question

So what size would be good for an indica to be transplanted from it's 4 inch pot? I've heard 8 inches tall, or second set of true leaves. And, should I go into a 3 gallon pot or a 5 gallon? I'm in the closet. Woah, wait I mean my plant is in the closet ROFL!

try doubling in size each time, you want to achieve a right thick root ball

thanks! makes sense