The paper you use can affect your entire painting. I want to say that paper is the most important material for success. Watercolor paper comes in different weights and textures, and each type has its own advantages and disadvantages. Thicker paper (300gsm and up) can handle small amounts of water without buckling, making it ideal for wet-on-wet techniques and multiple layers of paint. The most ideal is to use 425 gsm and above. Thinner paper (under 200gsm) is better for lighter washes and simpler sketches, but it may need to be taped down to prevent buckling when wet.
The texture of the paper also varies from rough to smooth. Rough paper has a more textured surface that can create interesting effects and give your painting a more rustic and dynamic feel. This paper is especially good for landscapes and subjects with a lot of texture. Medium grain paper offers a balanced surface that works well for most techniques and is often a good choice for general use. Smooth paper is perfect for detailed work and sharp lines, making it ideal for portraits and realistic paintings.
Another important factor is the material of the paper. Cotton paper is of higher quality and offers superior durability and water absorption, but it is usually more expensive. Cellulose or wood fiber paper is cheaper and can work well for practice and sketching, but may not have the same absorbency and durability as cotton paper.
Experiment with different types of paper to find what best suits your style and technique. Many artists find that they prefer different papers for different types of paintings, and it may be worth investing in high-quality paper for your most important works.