I had my first diagnostic laparoscopy last November. And I was also nervous and overwhelmed.
I would advise loose fitting underwear and bottoms (joggers or loose pj bottoms with loose waistbands) because you will be sore and bloated afterwards. Bring something to keep you entertained (book, headphone for music etc) if you have to wait, a change of clothes and something to sleep in, in case you are kept over night. Pack a small bag of anything you may need over night.
I suffered with constipation after the surgery which I hear is normal, I’d advice some sort of stool softener (not a stimulant, as this can cause cramps) to take as no doubt they work also prescribe you some codeine to go home with which will only constipate you further.
The discomfort from the gases was the worst part for me, peppermint tea helped me, but also laying down. This will also pass after the first couple days.
I hope this helps, good luck with everything!

Making sure you have lots of baggy clothing to wear is a good idea. Also, get one of those large, flexible ice packs. It helps with the air that gets trapped inside you during the surgery. It often ends up in your shoulder area.