First welcome to the game ^^ hope you enjoy your time
Ok to answer your questions :
1- you can do all jobs and explore all the possibilities in the game and classes you might get an interest in another class .
2- about the gil if you save up abit from just the main story and the side quests reward you might end up with more that 1mil by reaching 50 as for minions and glamour gear youll find minions a cross the game and glamour gear youll get the ability to do it after lvl 50
3- home work is needed tbh in dungs after lvl50 before you can speed read it or just ask if ylu get lucky in a party
4- linkshells it's basically a group of ppl not from the same FC gathered togther mostly used for raids and hunts
5- as far as i know no the game has no prob with that .
And once again enjoy your time in the game .