OK I've found a way to add GPs that could be used in ruffling.
1. Search 2;50;1;156::13
2. Edit the "50" into minus
3. Go to the Item ruffle and the single ruffle will give you GPs instead of charging you 50.
oops I didn't realize I misspelled raffle until your reply......m(_ _)m
The only demerit of this way is I have to edit the raffle price again every time I restart. But IT JUST WORKS.