Congrats on the new camper and welcome to the forum!
For sure the sewer hose - look at something like a Camco Rhinoflex 15'. I'd also add a clear 45 degree adapter as well so that you can see when the water is running clear from tanks.
I don't like the stubby electrical adapters like the one in that was in our kit - they have a tendency to heat up under heavier loads. Camco makes a good dog-bone style as well. I would also recommend investing in an electrical management system (EMS) such as progressive industries PTC30 or PTC50 depending on your amp rating. The EMS will protect your unit from a variety of undesirable electrical conditions and are well worth the $$.
We kept the white potable water hose but added another one as sometimes you have a longer run to the water faucet. Get a separate green hose to use for tank flushing only.
Never used the toilet chemicals - you'll find lots of discussion around those as well as RV TP vs Non-RV TP.
Good luck and happy camping!
TT: 2015 Jay Flight SLX 195RB Baja Edition
TV: 2014 RAM 1500 Bighorn CC, 5.7L Hemi, 3.21, Factory Air Suspension/Tow Pkg, Andersen WD/SC