how far in advance...

...did you order placecard holders? i want to get votives but not sure when to get them. i don't want to wait til the last minute, which it seems is when you get your final headcount. and our rsvp date is a month before the wedding. but i want plenty of time to make sure they come in. but of course, don't want to order too many/too little.
also same thing for anyone who used petal cones or bubbles after the ceremony. we're getting married in a church and who knows how many people will come to the ceremony vs the reception. how to estimate how many we'll need?