I highly recommend using card sleeves to protect your cards and make them easier to shuffle. The cards deteriorate and get dirty pretty quickly without them. Your deck will work far better if you are able to shuffle it easily.

Other accoutrements that many Magic players appreciate are deck boxes, playmats and dice. Playmats are foam placemats that make it easier for your cards to slide around the table. They’re not necessary but many players use them. Dice are useful for keeping tabs on the status of cards that change once in play, and sometimes also for tracking life totals. At my local store, and around the world, players use six-sided, twenty-sided, and sometimes eight, ten, or twelve-sided dice. I have some beautiful ones that are a beloved gift.

It is also useful to have a binder to display the rare cards that you are interested in showing for trades. This could be a nice thing to get for a friend to help them trade away cards they have rather than buying new ones.

During most games, a spell or effect will create tokens, which are permanents like a creature or an artifact. Booster packs come with token cards for token types generated in that set, so when you know which types your deck will need, you can try to locate some of those. It's also fine to use some other kind of card as tokens when you need to, although obviously it takes focus to keep track of what each one is.

There are other nifty accessories, but the last one you really need is cardboard boxes to hold cards you’re not using.