Hmmm good question... I think you should start with kid Goku not because of the order but because that's the way you get to know how it all started... Those episodes are so much fun!!!
Start with the Dragon Ball Series all the way until Dragon Ball Super. Never cared much for Dragon Ball GT. But if you want to watch it, that's your choice.
1. Whether I'd like it
And 2. Which series to watch first