GC, through dungeon playing and even PvPing, gives you enough GP to purchase all the equip you could ever want; the only real cash sinks are amulets and necklaces, where you often have to pay millions to get it to level 9.
Let's see... I'd give GC a 8/10. It's fun, it's awesome, but it needs something else other than fighting. Not that the fighting isn't fun.
Basically, you control a character street-fighter style; you use your attacks by chaining together arrow keys and Z keys. The key differences are that the screen is a lot bigger, it follows a storyline, and it has more equip, leveling, stuff like that. It's really fun and strategic, especially in PvP.
And let's see... Elesis is easy to play, Arme is slightly harder, and Lire is harder than Arme. But it really depends on your play style. I'd say, try all three and see which one you like the best.