Caster Marie, Edison, or Merlin

You should max Andersen's skills and save caster materials and qp. Andersen is enough for now until you pull Merlin, Waver or Tamamo. You can try for Waver or Tamamo at the guaranteed gacha coming soon.

If you don't get Waver, Marie is a decent alternative and Hans more than enough to Complete your team. Like the other guys said, i suggest raise Hans skill first. I also don't have any Waver on my main ( it's more than a year T_T ) and Hans never let me down, he even save my asses more than i expected. I also have Helena which is like Marie cas, she's also a decent substitute for Waver.

Like you, i also have Edison ( this man really funny ). Well Edison is pretty Durable caster. He has different kit, a unique one and great at demolishing assassin or ghost mooks easily, if you don't have any wave clearing one. Edison skill usage is very gimmicky, so be wise using him and i really not recommended raising him first.

I assume you are talking about summer Marie. As someone who does have a maxed out Waver, I still use Marie quite a lot. She is incredibly survivable with her 3 hit evasion and her turn based heal. It takes a lot to bring her down. Her NP charge isn’t bad and has a decent effect. I would prioritize her over Edison. It’s still a bit till Merlin’s banner and she could be of use to you till then. Hopefully you’ll draw him but if not, you’ll at least have her leveled up already. With her and Anderson leveled up you should be fine.

Hans > caster Marie > Edison

Pair caster Marie with male servants like Kintoki is a good idea. Then you can have her 1-2 skill maxed.

Edison is decent for his 3rd skill and NP effect. But you dont have to skilled up to lv10. Lv60 is enough before Marie and Hans' maxed skills.

And dont rely on any quick-based servants except Kintoki as for Caster boss killer and Lancelot as for farming. Their shinning time is almost 2 years later when Skadi's come.