I'm going to disagree with everyone else and say that, if you're serious about graphic design or digital illustration, you should get a tablet ASAP.
If you're the creative type, then it's unlikely that your first experience drawing is going to be in a digital media, as you were probably exposed to analog media in art classes likely as early as kindergarten or grade school. And I do think you should take traditional art classes to build your foundations, as those courses generally aren't taught using digital media. But that's more to do with tradition and practicality than anything else. (It's easier to furnish a class with pencil/paper than it is to provide each student with a digitizing tablet. And not all students will have a tablet to practice on at home.)
Yes, analog media has a lot of qualities that can't be replicated by digital media, but the reverse is also true. And if you're going to spend most of your career drawing digitally, then getting accustomed to the feel of a tablet as soon as possible is going to be much more beneficial than learning the nuances of physical media. And it does take some time to get used to drawing with a digitizer tablet.
And while a high end tablet may be quite expensive, a cheap entry-level tablet like the Bamboo may actually save you money. Art materials aren't cheap, and if you're drawing/painting all the time, it quickly adds up. So digital media lets you get in more practice without spending as much money.
Digital media is also more beginner-friendly in some ways. The biggest reason is that there's no undo button for your physical canvas. Sure, you can erase a pencil sketch, but you can only do that so much before it starts to wear down the paper. There are no such problems with digital media. You also don't have to worry about making one mistake and ruining an entire piece, or smearing, or having your paint dry prematurely, or not being able to match a color you used in your last session, etc. There's also less cleanup if you're doing a digital painting versus analog.
All of the above reasons might make one inclined to practice more using digital than if they only had access to physical media (I know it did for me). That isn't to say you shouldn't bother with physical media, just that you should have both options available early on. The most important thing is that you set yourself up so that you can, and are motivated to, practice as much as possible. If you have both a tablet and a sketch pad, you can draw on the media of your choice whenever the urge strikes you.