Blacksmithing is a great profession, and for some classes it would be a very wise decision to make ffxi gil blacksmithing their profession.
Mining should definitely be taken as your second profession if you decide to be a blacksmith because it will save you a lot of gold. Leveling blacksmithing is quite expensive even if you are a miner and doing it without it will costs you thousands of additional gold.
Blacksmithing would be a perfect choice, especially for the plate users and melee DPS classes since most of the goodies that can be made only have a purpose for these classes.
It must also be sad that the best craft-able and usable items come in the end. Even though you might find some armor, items and weaponry that you are able to craft while you level worth equipping to boost your character a bit.
Most of you probably know you need a Blacksmith Hammer to craft items and that most items can only be crafted at a forge. Forges can be found in all the major cities though, as well as in many smaller villages.