If you want to use vlans, then go all vlans and learn how to use them. Allows for future growth.
thus one bridge all subnets as vlans. And dont touch the default vlan1 on the bridge leave as is. Use other vlans for all your subnets carrying actual data.
this is a good starter…http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1