
I personally like the rancor sword. Personally, if you can get new characters like Linnea, newer characters tend to be more powerful than older ones. Artifacts will impact your experience a lot so always make sure to upgrade the four star ones. Three star ones are useless, they are good, but it’s better to use them as upgrade material.
for picking artifacts and weapons, i'd suggest looking at the respective keqingmains website for the character you're trying to build! google "keqingmains chongyun" for instance. as for characters, it really depends on who you have. there are some must-upgrades that will last you throughout the entire game (bennett, sucrose, xiangling, xingqiu, fischl). as other person said though, generally newer 5*s are what should be focused on since they are more powerful than others due to powercreep.