A Photoshop or Illustrator course will not make you a better Graphic Designer; yes, it will teach you how to use the software that industry Graphic Designers use but the software is not the problem. The principles are.
Design tools are just that, tools. Knowing your way around Adobe Illustrator is a mechanical skill, the same way knowing how to use a hammer is a mechanical skill. Knowing how to use a hammer does not make you a carpenter just as knowing how to use Photoshop does not make you a designer. The principles of design are the foundation that sits underneath every good piece of work, and they are where most beginner portfolios fall short, mine included when I was starting out.
The good news is that you can learn these principles and become a great designer.
There is no universally agreed-upon number of principles (you will find lists ranging from 7 to 13 depending on where you look), but the ones below are the most consistently referenced across the field. Learn these, and you will have a framework for making decisions about any design problem you face.

Graphic Design Principles

1. Emphasis is about creating a focal point. Every design needs one element that the viewer’s eye goes to first. If everything in your design carries equal weight, nothing stands out, and the viewer has no idea where to look.
2. Contrast is how different elements are from one another: light versus dark, large versus small, bold versus thin. It creates visual interest, supports emphasis, and when applied to text and background, is a legal accessibility requirement for digital products in many countries.
3. Balance is the visual distribution of weight in a composition. It can be symmetrical, which feels formal and structured, or asymmetrical, which feels more dynamic. A balanced design feels stable; an unbalanced one feels uncomfortable, unless that discomfort is intentional.
4. Alignment creates order. Every element should have a visual connection to something else on the page. Random placement makes work look unpolished regardless of how strong the individual elements are. Use a grid.
5. Repetition ties a design together. Repeating colours, typefaces, shapes, and spacing creates consistency and is the reason a well-designed brand feels cohesive across every touchpoint.
   Proportion is the size relationship between elements. When things are well-proportioned, a design feels natural. When they are not, something feels off even if the viewer cannot name exactly why. The golden ratio and the rule of thirds are useful reference points here.
6. Hierarchy establishes the order in which information should be read or noticed. It guides the viewer through the design deliberately. Typography does a lot of the heavy lifting: the relationship between headings, subheadings, and body text creates a reading path that should never make someone work to figure out where to look next.
7. White space is not empty space, it is an active design element. It gives elements room to breathe and makes a design feel confident and considered. Overcrowded designs feel amateur. Generous white space feels professional.
8. Movement is the way a design guides the viewer’s eye through a composition. Through lines, shapes, gradients, and the arrangement of elements, a designer creates a deliberate visual path, which is especially important in layouts with a lot of information.
9. Unity is the goal all the other principles are working toward. A unified design is one where every element feels like it belongs, where typefaces, colours, shapes, spacing, and imagery all feel like they are part of the same visual language/they exist in the same universe.

A Note on Breaking the Rules
These principles are not absolute laws. Designers break them deliberately all the time to create tension, surprise, or visual interest. But you need to understand a rule before you can try to break it effectively. Designs that do not respect these principles will look like amateur work and will fail at delivering the intended purpose.
Study the principles, apply them, and then once you know them well enough, experiment with pushing against them. That is where personal style starts to develop.

Where to Go From Here
Reading and researching about the principles is a start, but the only way to really internalise them is to practise applying them. Pick up any design you have done before and evaluate it against each principle listed here. Is the hierarchy clear? Is there a focal point? Does the alignment feel intentional? Is there enough white space? That kind of critical self-evaluation is one of the fastest ways to grow.
If you want to go deeper, The Non-Designer’s Design Book by Robin Williams is one of the most accessible and practical introductions to these principles, and worth reading cover to cover.