Welcome. You ask many good questions! Honestly your first saber will be special for you no matter what it is, but you will want to keep it intact no matter what. You will not want to experiment on it. When the team gets back from Dragon*Con in Georgia there will be an options called "Grab Bag." THOSE are sabers for Frankensaber experiments.
Honestly where you start it up to you. My first saber was an old PVC Omen, then I slowly upgraded to a Metal Hilt and just recently got my first saber with sound from US. If you love the Shock and can afford it I say GO FOR IT! But that's just little old me.
If you want to be able to change your blade color then you either want RGB or you want Quick Disconnect. If you're really into having 7 full colors at the push of a button then you are right to go RGB, if you are more interested in two specific colors then get the QD.
Plus, if you want to custom build sabers you should go to
www.youtube.com/greytale (that's Master Novastar's channel). He's got some tips on good ways to start out on building.
My suggestions summary: RGB Shock with all the bells and whistles you desire and wait to start builing. Just enjoy your first saber.
Cheers