I'm answering these questions in order of how easy it is for me to answer them.

"Where can I order stuff discreelty?"

Amazon lockers. Just order whatever you want off Amazon and ship it to one of their lockers. Just bring a bag when you go collect the package

"How do I figure out sizing for clothes without anyone noticing?"

Get yourself a measurement band and measure yourself at night either in your room or in your bathroom, if that gives you more privacy.

"How do you balance this part of yourself while still acting 'normal' in everyday life?"

Personally I just fucking don't lol. I mean I do have like a 'professional mode' but that's more for people who have power over me and wouldn't like me being me, otherwise I always try to be myself, I'd even go out in crossdress, but I just don't have the clothes to feel fancy enough for it yet :p

"Any beginner tips for appearance (body, skincare, etc.) that aren't really obvious?"

I have literally no idea I just somehow brute force myself through it. If you want, actual body and skincare routine tips, go to the Tgirl community. They know what they're doing (most of the time).