From an ESD point of view it is very preferable to make the GND connection first.
When using standard 0.1" connectors you can push the GND pin out a bit, so it makes first contact.
Putting in small series resistors help a lot in preventing ESD damage and also help in preventing damage from short circuits. But they may limit the baudrate, especially on long cables.
With a 5 pin connector you can have 2 GND pins on the outside. Then two pis for Rx or Tx, and a single pin in the middle. This would make your connector reversible.
I suggest the GND pins on the outside, because it is likely the connector will be first inserted under a slight angle and the outside pins make first contact then.