Advanced Ticket for Tateyama Kurobe Alpine

Hi,
I want to do the Tateyama Kurobe Alpine Route one-way from Ogizawa station on Tuesday May 13, but the advanced tickets at the official web site are mostly sold out. Only some left for 7.30AM departure which is too early for me, since I'm coming from Matsumoto. Should I buy the ticket and board later bus? Or should I still go and purchase the ticket at the station? What time should I arrive at the station that's not too late and could have a decent experience?

/JL