Yes, shop=gift is okay !
I've made a few changes again.
This photo shows the gatehouse and entrance:
https://buskompass.de/wp-content/uploads/2022/07/220101ck555838-1-20030711280DR_Raben_Flaeming_Burg_Rabenstein-first1234_orig.png
You have to go through the same door if you want to go to the small museum that includes the tower or if you just want to buy some souvenirs there. Also the opening hours are the same and it is also the same vendor who sells tickets and a few other things.
It's in this gatehouse. Go up the stairs on the right and a bit on the wall to the entrance.