You would get the 90 days award right away.

As for your second question, if there are any gaps in your current gear the CG gear is a viable option. Even more if you are leveling multiple classes, as they can be equiped by almost any class. Crafted gear is probably better, but if you don't have any gil to spend (or don't want to spend it) CG gear is definitely an option. If all of your gear is still up to date there is little reason to replace them though.