Hi and welcome
Not all royals go on starving sprees and the ones that do....do it for lots of different reasons be it breeding season/they're not feeling secure in their enclosures/wrong or incorrect husbandry etc
If you go for a baby then make sure its a reliable feeder before its sold to you and obviously its better to have your RUB set up and running for a week before you actually get it so that you are certain all temps etc are perfect so theres no messing about when the little guy is moved in to it and it can settle right in there.
Pack the rub out with lots of cover...i.e. hides/plants/cover so it will feel secure almost immediately after a few days of settling into its new surroundings and also avoid handling for a week or 2 to allow to settle well. Its not always important to leave all snakes to settle in, but you never know what type of character yours will have so its best to let it have this time to settle just incase it has a nervy/stressy personality (some arnt) i have and adult and a young baby - both males and they are both really confident and outgoing and have fed from day one and love to come out for handling, so much so that sometimes i open their viv or rub....they are happy to come out to me by themselves....so not all are stressy panic bags!
Royals are lovely snakes and mine are often out during the day too.
habistat are a good make of mat and stat....take a look on "surrey pet supplies" website....you wont find stuff much cheaper or you could try "ebay" for mats. if youre planning on 300g or there abouts...i would say get an 18ltr rub, its a better shape then a 12ltr and you can fit a bit more decor in there and a nice ceramic dog bowl (small) big enough for it to soak in if it needs to.