it can be one guild per city a day (3 a day, one from each city), all guilds from any city a day (18 a day from any city), each city only posts from guilds within that city (~6 a day from each city), or any number from each city (lets say limsa offers 6 quests from the guilds in limsa, u can only pick 1, or they offer all 18 but you can only pick 8 like leves)

all we know is 1-you start the quest in the adventurer's guild board and 2-one guild per day, so it's impossible to do 2 gladiator quests in one day. but can you do gladiator/pugilist or glad/pugilist/miner in one day? it's possible. we only get one npc in each city to hand out battle leves, but it's not like we can only do one leve per city. we only have one adventurers guild board but it doesn't necessarily mean one a day, it could list options. now, it seems to me one quest a day, since you can do each quest in any class "awarded to the active class at time of completion" but noone knows for sure, the description can be interpreted a number of ways.