Level 25 maybe? I don't remember, you'll buy it with the seals you earn from doing grand company quests.

Not even speak to a guild, just put on a different weapon. Put on a bow, you're an archer. Put on an axe, you're a marauder.

You'll be able to find nodes for any gathering with abilities gained on those jobs. There are also resource sites if you care to find them, that will show all the possible spots.

If you're gettin cream really bad, upgrade your armor. If not, just keep your weapon upgraded.

~and y/w