Hmm, the only things I would do for sure are get the silver bars and 1 of each flight suit color done before you actually promote, and the other two done after. I'll be an LT in about a month and I never have had my blues sewn or gotten hard or soft shoulder boards. Covid probably had a bit to do with not needing the fancier uniforms but I woudlent buy every little thing up front. And if you do, save the receipts for the JG boards, they're like 60-70$ for both and you may never actually need them.
YMMV, but you don't work in DC, if you catch my drift.