You do not need to level all crafts to 50 or even 15. With just Goldsmith and Carpenter up to 2.4, I was able to make plenty.

To make money any time, in any MMO, you have to observe the market board/AH/Economy on each specific server. For starters, observe how much gil is flowing in each of the professions markets.

What may be profitable on one server may not be on another. The lack of goldsmiths on one server will make goldsmith profession goods, pricey and on high demand, while on servers with an overload of goldsmiths it will make their goods cheap and on low demand.

The only way to get an idea of what is happening on each server is that you take the time to look in to what your server sits around. Once you figure out whats happening, which profession you should choose will be pretty evident.

In summary, find the profession with the highest demand and highest gil flow on your server. Take it up. When the highest demand and gil flow changes, you change with it.