hey ill share a bit of my preplanning mindset:
i think its best to pack as light as you can, with baggage fees you may be bringing many unnessecary items. most of what you need can and should be bought there
your absolute necessities should be: your passport, your money, whatever documents you need.
in terms of clothing: it seems that its best to bring clothes that are easy to put on/ off like trackies or shorts sweatpants
for shoes the less lacing the better, sandals and slip ons
whatever you need for the climate there (rain jacket/ coat) ( although side note if youre flying to a place in the winter to get LL done that might be an icy slipping hazzard)
maybe bring a pair of pant you really like but are too long for you for motivation
most of these items you can buy on location. if youre in the states there are HEAPS of outlet stores that you can get good clothes cheap
as for vitamins/ supplements i would do research before hand to see whats available in youre chosen city. if youre planning your surgery in the states, supplements are very cheap there. as most LL docs are located where its warm all year round dont forget to invest in sunscreen( no one wants to get skin cancer whilst on their journey getting taller) some supplements like Vit d calcium Vit K and collagen, wouldnt hurt to start before your lengthening journey.
in terms of medications, the only two main ones will be your pain management and anticoagulant. these are the ones that will be where you can really save money. for anticoagulation paley said on his site that he uses xarelto, which is rivaroxaban. the hard part will be getting your pain killers, which will be opiates. its seem the most commonly prescribed one amongst us LL docs is norco, which is a mix of acetaminofen (tylenol) and hydrocodone. i dont know how to help you there because no doctor in their right mind would write you an rx for them you may have to just bite the bullet and pay for those drugs
in addition bring which ever medications you are also taking( bring 3 months worth or however long youre staying)
in terms of passing the time: definetly bring a computer, gaming system if you can fit it ( remember that hauling eveything back while you are in a weakened state may pose a probem, i know whenever i fly with my ps4 i cant put it in checked luggage and have to take it out every time i go through security which SUCKS. on that note maybe get a switch)
everything else i think would be much easier for you to buy and leave in your destination: like get some cheap rehab equipment like bands. check how much a walker would be online vs buying on location.also i think two things you should definely invest in :a bidet and a squatty potty
sorry if this was a little scattered. writing is not my strong suit.