I started play like month ago and finished every quest in fate zero event, which rewards would be the best for new player to exchange?
It depends on what servants you want to ascend or upgrade their skills.
I suggest searching here for those servants, look at the materials they need and buy them.
You can also make notes of the materials they need or bookmark their pages on your browser if you want to be thorough. Prioritize ascension materials over skills.
The thing is that I dont have any good servant yet, I didnt pull for anything. My first rolls are Tamamo Cat, Carmilla and I have Iri from event. So should I focus on maxing them or just store some overall good stuff.
Carmilla is good, so definitely try to max her.
Tamamo Cat is a farming servant, and farming is something that you'll be doing alot of in this game, but the problem is that she's easily replaceable. Personally, I have her but never bothered leveling her because I liked using Hans + Kiyohime + AoE Support combo instead, since I don't have Kaleidoscope CEs, I have to make up for the party's NP generation by adding in Hans since he provides 3 arts cards for his teammates, instead of Tamamo Cat who only has 1 arts card.
Also, you shouldn't completely ignore lower star servants, Robin Hood is known for having a powerful single target NP that will help you alot against Saber bosses, Hans Christian Andersen is a really good Caster and far better than Irisviel in my opinion, he has an NP which gives your party health regen, and that will help your servants survive during tough boss battles. David's 2nd skill will give a party wide 1 time evade which is really useful when an enemy is about use their Noble phantasm or has an AoE attack ready for next turn, and Eruyale is famous for being helpful in the upcoming story chapter.
I recommend ascending these servants, especially Hans and David. Unless you'll be spending money on this game right now, waiting for 4-5 star servants to show up so you can use the materials on them isn't viable and will keep you from progressing in the game, since you'll be saving up your quartz for banners you really want and those could take months to arrive.
Edit: I also agree with what fooming said, if you think you can, you should try to get everything from event shops, although the problem with this is that it will take alot of your time and could make the game really grindy and not so fun in my experience, so you should leave that to your own judgment.
Thanks for explain, I have no idea yet which servent is good or bad. I
EDIT: I looked for trier list and i have Medea from S ranks is she worth leveling now?
Medea is the type that specialises in her own field, which is removing buffs on enemies who like to use them alot, she can spam her NP constantly for that purpose.
She's good against those enemies, but in alot of typical battles, you may not find an use for her and would be better off with another servant instead. I'm caught up with the story myself but haven't used her much.
I'd say NA isn't at that stage of the game yet, but I've heard from JP players that there will be alot more enemies who like to use buffs/debuffs in the future, so maybe level her eventually, but no need to make her a priority imo.
I would prioritize the Experience cards first and then look into which ascension materials you need for your team and go for those second.
Everything you can get.
You might not need them now, but you will need them later, exchanging items in event shops is way way way more efficient than grinding to get them. Always advisable to clear the event item shop, whether you are new player or old.
