Suck it up.
You f*ed up, and you're going to have to live with it. It sucks.
Byakuya is good for PvP, but like every one else has already said:
If you don't pay, go PvE setup.
By increasing your PvE formation and getting kills in Ryoka, you'll naturally have more silver to do stuff and consequently become strong in the Arena.
when i dismiss komamura because i had toshiro i was sure i got 400 golden reiashi back. i remember clearly i had 450 golden reiashi and i dismissed komamura. After a while, when i went to tavern to get more golden reiashi, I yelled "HOLY SHIT!" when i saw golden reiashi is higher than i had. I believed it have to do with dismissing komamura. NOBODY TOLD ME I GET GR BACK......