Answer:
I'm a small ring shaped fried cake, often with bavarian cream or fruit filling, and sometimes covered in icing and sprinkles.
Makes dough grow
Take one royal word in the plural and make it singular by adding one letter
Low on cash? Pick out items from this rack.
The line a runner strives to reach
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.