Curation Rewards - Vote at what time?

hi guys,

i've read some guides about how to get curation rewards and got 2 questions about it:

some guides say, i should vote as soon as possible to be the first one. other guides say i should wait until 30 minutes and vote then.

can you tell me how it really works?

and how much steempower do i need to have until this is valuable?

thanks in advance!