Snow Raphael covers the B frame ATK/DEF debuff for your water team, while Ryu-oh covers A frame ATK/DEF debuff, they work VERY well together and with Rudra, you can do serious damage but I don't say it's worth getting D'art, since that's pretty much the same as having Ryu-Oh/Mordred, they don't really mix well. I'd say go for Arthur or Hercules weapon, since you're new I don't see you getting Shingen any time soon.
Hephaestus is super good for a SR. You can't expect to get so much so soon.
Try to join a union and get rewards that way, since UE starts tomorrow night.
do gemchas too to unlock some R fire/dark girls if you haven't already, watch/skip encounters, etc and try to draw girls with jewels whether it's single or 10 chain pulls.
fire raids are apparently x15 up on magic jewel gacha right now, so better now than later.