A CPU paired with a dedicated GPU will always bring the best gaming performance. However, this will increase the overall cost of the build.
Both components are equally important for gaming and bringing that balance to your PC in general. While many consider the CPU to be the most important aspect of a PC, you cant enjoy the majority of games without a dedicated graphics card. A GPU has a separate chip, its own power budget, its own cooling, and its own memory, simply giving you more power to play with.
Whether you buy a dedicated GPU or not is linked to your budget, as this will often incur the most cost.