Hi Tank Girl - Good start....
For 80 litres of water, you would require around 20 to 25kg's of live rock (a quarter to a third worth).... BUT, you can always "build up" to that - I know that 20kg's worth of live rock is QUITE expensive.
A few larger pieces would be "nice" - especially some flatter pieces, that you can "build" a network of caves for the fish to hide in/sleep in....
The "live sand" that you bought, contains bacteria of all sorts - BUT, not any micro fauna yet.
Getting a "handful of live sand" means that you get some seeding sand - full of worms/amphipods/copepods/ (possibly) micro brittle stars, etc....
This assists with the cycling time.... BUT - it is not a necessity - it will happen as soon as you have some live rock in the tank, as well... it might/will just just take a wee bit longer.
Good luck, and don't be scarce with the pics now, hey!