New to selling – brand/tm and others

Hello,

I want to start my own brand of clothing and out the brand name on each one. Do you think I should register the branding as a trademark first before publishing the store?

Would doing a copyright on the logos be better?

Also for listings, if I have a shirt, hoodie, tank etc all with the same design, should I list them as all individual listings having only sizes and colors as variations? (And if I have 20 designs that would be 20 x 3 items = 60 listings?)