Yes, you need them. LOL
Everything is an investment, so I say go for it and have fun if you decide it's something you would enjoy as a hobby. Before you do, go out and buy a few, and try them out first. Just make sure you buy them closer to their color family and numbers (E31, E35, E37, E39), etc so you will have a better time blending from lighter to darker shades.
Copic has a very large user community, even in the card making hobby, so you will have plenty of help and inspirations. Alot of blogs will give you color combos so you can use that as a guide.
I list the color combos I use for my Copics, lately I've been doing a set of tutorial videos on my blog so you can follow along at your own pace. I have a list of useful Copic links the sidebar of my blog to help you out.
Oozak.com sells his Copics for $4.15 if you sign up as a member (it's free). And he ships free with $50 purchase. I shop there, and shipping is extremely fast.
Good luck! ;)