Good news is yes, you can take the costume off. Guide on how to do this:
Un/equipping Guide Video:
I’ll also link the FAQs for the costumes as I HIGHLY recommend you (and others) have a read!
Now! To answer your question more directly:
Good news is you only need one Costume Pattern you can eat the other one without any issues (see FAQ for how)
Mats will eventually come. They just take time. Check my response here about my advice for newer players still building their roster & depth:
Materials will come in time… Just gotta be patient & keep plugging away. Best place to get materials is from titans so I recommend joining an alliance which challenges you in their titan level!
This guide goes into more details about titans and materials:
you can eat the other one without any issues (see FAQ for how)