I participated last year, so I'll share my observations.
The host will send her address info closer to time to send your seeds, which covers your first questions.
Most of the seeds last year were in those small ziploc bags (you can get them in Walmart craft section by the bead and jewelry making supplies) but some were in commercial envelopes or handmade ones.
There doesn't seem to be a minimum, since people are dibbing, they can decide whether it's worth it ir not. From experience, larger quantities of common seed is expected, but rare seeds may only have half a dozen in a pack.
Every day you get so many tickets, which goes up each day (so day one you get 3, day two you get 5, etc.) Also, for each packet you offer that someone claims, you earn more tickets.
Don't know what the average number per player is, but I know it's more than will fit in your garden. I passed along a ton to other gardeners, and still have more than enough for a dozen gardens.
