The surface you choose
Here is a painting. It's not done but it's on it's way to biscuits. I'd say 80%. The thing that is important about this is the surface and how it affects the way I (we, you) paint. I saw a painting at the Orlando Museum of Art a long time ago by Frank Benson of a lily pond with some trees. It was all about the surface and the paint. The canvas was broad weave and I mean burlap broad, big chunky knots of linen and a terrain like the Grand Tetons. So... I went out and bought this roll of unprimed Belgian linen, broad weave. It was pricey. and this was years ago. The first time I worked with it (again unprimed) I just gessoed the stretched canvas. Not the way to go. It needs to be sized or sealed. This time I consulted a specialist, the local art store dude, who said, "you need to size it with rabbit skin glue or this stuff called GAC100." I have an aversion to anything related to cute animals, even if it's not, so I went with the GAC and then gessoed the canvas two or three times. The broad weave helps the strokes to skip across the plane of the surface which is both helpful and a hindrance depending on whether you work wet into wet or wet into dry. The thing about any surface is that it changes the way you paint. It alters the way the paint comes off the brush and how wet paint interacts with wet or how wet interacts with dry. The right surface will change your painting life or confound you. The one you need is for you to find. It makes a huge difference, I swear. I have worked on everything from raw wood to exotic pastel papers to cotton duck, belgian linen and treated paper. One way to get a variety pack is to order a sampler from somebody like WindRiverarts
There are other sources for sure but these guys have a poopoo platter of a canvas pack that might help you figure it out. I order a lot of panels from them and they are great people. A painting surface needs to have the right combination of of bumps at the correct spacing and the appropriate height, for your kind of paint handling. The absorbancy is really important too. While it's important ot find a surface and stick with it, it's also important to try different things to see what happens. It could just change your life forever.