In my humble opinion, quality is better than quantity. Many tutorials will tell you that if you're a beginner, use any paint you want, any pencil crayons you want, or any substrate you want. It's just for practice and learning so what's the big deal?
Here's the big deal....if you've learned with low quality products and transition to professional products, the colors will mix differently, dry differently, and the application will go on differently, and you will end up learning all over again. You might want a certain effect in your art but can't achieve it because the materials are limited. "This isn't blending well", "This doesn't cover well", "My paint looks muddy". All those things could be a lack of experience, but it also has a lot to do with your material. If you're learning and get frustrated you could end up giving up because you feel like you suck when the reality is, it could be your materials! And last, if you've been doing art for a while and are still using student grade materials, you're art may likely not last as long or be as vibrant as artists who use professional materials.
So the top four things you should invest in as an artist are:
1. Mediums. These include things like, graphites, pastels (chalk or oil), paints (acrylic, watercolor, guache, oil, spays), colored pencils, inks, etc.
Student grade vs professional grade. Student grade mediums tend to have less pigment (color) and include additives to make the product cheaper to purchase. Because of the lack of pigment, certain colors may not even be available for purchase, while other colors are less saturated and seem chalky or are have a slightly different hue than a professional grade comparison. Since this is a general observation, I won't get into specifics about each medium since inks, vs paints, vs pencils are all made very differently. However if you'd like to test out this suggestion, go for it. Get a cheep medium, compare it with a professional medium and see what you think.
2. Substrates. This is what you draw on, paint on, print on etc. Papers, canvases, wood panels all affect how your medium is applied and how long it will last. For example, some paper is not acid free. If you use this type of paper for drawing or printmaking, the paper will yellow and crumble over time. Walmart brand water color paper is a lot different than Strathmore watercolor paper. The lower quality paper will not allow your watercolor to be saturated into the paper so there is more chance of dripping and less ability to blend. For canvasses, a heavy weight material will not rip or warp as easily as thin canvasses. The professional quality canvass will also outlast it's lower quality counterpart.
3. Applicators. This is what you use to apply your medium to your substrate. Usually this involves a brush or a roller but can also refer to blenders for pencils or markers, I learned to apply acrylics with a hog hair brush from the dollar store. This might be okay for a specific style of art but if you want smooth blending, I'd go for synthetic. Also, cheaply made brushes loose the hair often, leaving it on your painting where you have to pick it off and the glue that attaches the ferrule (metal or plastic tip) to the handle of the brush dries out and the handle just dislodges from the ferrule.
4. Organizers. This suggestion may not affect the quality of your work but I do feel it is quite important. I have to be honest here. I am not the most organized person in the world. But I certainly recognize the need for it. I can't count the times where I've asked myself, "now where did I put that?". Being organized can save you so much time (and sometimes money if you have to repurchase what you've lost). Organizers are not just for your materials, they're also for your finished work. You don't want a finished piece you're going to sell get damaged because it was lying on the floor or fell off a shelf or was leaning against a heat vent and got warped. The more time you have, the more artwork you can do! The more artwork you have, the more you can sell. Get the idea?
I know I've kept this quite general and in the future, I will write about specific mediums, substrates, and applicators. In the meantime, attempt to transition your materials if you can and you'll see a huge difference.