Looking for that perfect deck is an amazing journey and extremely personal. There is no right or wrong deck. You can have one deck or you can have many. Similar to how one might choose a lover, I recommend that your first deck be something that pleases and inspires you. The deck you choose should draw you in, warm your heart, while tempting you to touch them all the time.
Admittedly, I have several decks but only a couple that I read with on a regular basis. I have one personal deck that I use just for myself. This deck pretty much goes everywhere I go. However, depending on my mood or my question I may choose one of my other themed or artistic decks. I also have a deck that I use when I read for clients. For my personal deck I use the medium Illuminated Tarot. The deck I use for professional readings is the large Illuminated Tarot. Both of these decks were handmade by Carol Herzer; recolored versions of the Rider-Waite-Smith deck. I paid the extra money for the iridescent paint which was well worth the money. Carol's amazing use of color is magical, expressive, and captivating. Years later they are still my favorite.
Depending on how far you wish to take your tarot study, you may eventually choose to purchase a more traditional deck. Perhaps something based on the Golden Dawn or Thelemic system would help you get a better grasp of Tarot. Or if you're into psychology, something with a Jungian flavor might help you along your tarot path. For meditation and study purposes I use the B.O.T.A. Tarot deck (which I colored myself), the Rider-Waite Tarot Deck, and the Golden Dawn Tarot.
The deck I used for the first eight years of my tarot study was the Thoth Tarot, painted by Lady Frieda Harris, under the direction of Aleister Crowley. People seem to love this deck or hate it. Either way, the Thoth deck manages to standout, separating itself from the rest of the decks. As for me, I immediately found its imagery vibrant, hypnotic, and seemingly without end. One can easily get lost in them. Professionally speaking, before moving onto the Rider-Waite, I found reading clients with my Thoth deck energetically draining. Ultimately it is the Golden Dawn system that I prefer now and the Rider-Waite tarot deck that I use for instruction.
Supporting local metaphysical shops and bookstores in your area is always fun and offers instant gratification. In my area, its shops such as Eclectic By Nature in Greensboro and Gaea Gifts in Asheville, North Carolina that I tend to frequent most. But if I can't find what I'm looking for locally I will inevitably find my way to online shopping sites such as Amazon or eBay. It's almost too convenient.
There are so many wonderful aspects to Tarot, all you really have to do is pick one and see where it leads. Some people are drawn to numerology, for some it's astrology, for others it's the four elements, and the list goes on. Where you decide to start or how far you decide to take your relationship with Tarot is personal and entirely up to you. Whatever your interest in the cards, you will never run out of resources and you will never learn everything there is to learn about Tarot. There really is no end to it.
I can easily lose myself on Aeclectic Tarot, which is probably one of my favorite sites for perusing various tarot and oracle decks. I also find sites such as B.O.T.A. and American Tarot Association, which I am also a member, most helpful.
Wherever or however you decide to purchase your cards, your first deck should be something that you are drawn to, something that beckons you to take a closer look.