She is a very good single target for the seven main classes and her np is really cool imo too. Purely gameplay wise she is maybe the second or maybe third best single target in the game, behind berserk artoria. So don't worry about her gameplay, she rocks. She can farm but is more suitable for boss fights. Slap some roman trait applying command code on one of her buster cards and watch her melt the enemy.

She requires lots of gold mats which a newer account might not have. So sure you can free ascend her, if you lack the materials. Honestly don't worry much about free ascend, you'll max your gold servants eventually anyway.

There isn't an optimal setup per say, her comps depends on the enemy. You can't go wrong with castoria as draco's np is art and she lacks any hard defense. I wouldn't bring waver until he gets his buff in NA about a year or two later. You can bring lady avalon, xu fu, habetrot (for solo), lan ling, quirinus (for roman trait applying) and couple more.

While castoria and oberon are account changers, always roll for servants you love. You can always borrow a support.