It's my 1 year Subeta birthday, and i want to do a 'reverse gift giving' thing in the SB where I give people gifts instead of them giving me things.

Part of it is a "If you say this first, you get something" type thing (what i want to do exactly is say "If you want one of the 'cures' from the Millionaire center, the first person to say the name of which one gets it".)

Can I do that?

I'm pretty sure you can. There's a special forum for giving stuff away, go look at it and see what people do.

the rules say:

No Begging Do not ask other users to give you items, pets, sP, or services unless they have offered it as a gift or part of a giveaway.

This leads me to think that holding a giveaway in the SB is allowed. You may want to make a ticket to ask a staff member though, to be safe

That would make sense :D