I'd recommend;
Final Fantasy VII: Crisis Core - Not so much customisation but there is leveling up, gaining higher stats, and you can change equipment and techniques you can use. Ofc, this is Final Fantasy, so the storyline is top notch and will engross you all the way through.
Final Fantasy Dissidia - Not so much an RPG but there is a storyline for every character. However, Dissidia has much more customisation than Crisis Core and you can use a much wider range of techniques and a much wider range of equipment. It is though more of a fighting game than an RPG but it's something to look into.