Caring for a baby hognose, help

Hello,
I am getting my first snake in the next week or so. I've done a lot of research trying to be well prepared. I'm concerned about housing though for a baby. I've read that its important to keep young hoggies in a small enclosure to not stress them out, but I'm worried about maintaining heat and lighting in a small enclosure. How do I light and heat a RUB with the correct gradient when the box is so small. I'm also not seeing much info on when I can safely move him up to a larger enclosure. I have an exo terra med-low tank setup for him, but I have realized its far too large. According to the breeder the snake I'm getting is about 3months old and 13g.

Sorry for the beginner questions. I'm terrified of doing something wrong.
Astraea