Common practice would be a couple of transplants. Maybe from the cup to a 1 gallon pot and then a 5 gallon pot. If you have a good root ball you could skip the intermediate transplant. Something about transplanting seems to stimulate growth if it's done right. Do it wrong and you will stunt it.
When the foliage spreads out past the pot is usually a sign it's ready, that and a healthy rootball. I like to start in a clear cup inside of a red cup. Then you can pull it out and see how the roots are developing.
If the plant is growing well it usually takes only a week before it's ready for the last transplant.
Your plant looks pretty healthy albeit a little slow growing. Wait a bit more before you transplant. I can sort of see some decent roots near the bottom.Looks like it's getting ready to really start growing. Good luck and happy growing.