To get anima you have to go back to baaj temple, fight geosagno, the skeleton fish guy, and swim into a "hole" you see. You must find the treasure in all temples. To beat Sin I gave Yuna doublecast and ultima. Revisit all the temples to get various spheres, it makes getting those spheres alot easier. Have Yuna equip Nirvana for one mp cost. Keep using double cast and ultima, it's cheap, but it works. That move also works on the final boss.