I'm also learning watercolours it's been a year since I started (previously acrylics) so I'm not an expert by any means, but I can pass on some of the things I've learned so far that I think are important:
Paper
I find that this is what makes the most difference to the experience: wet on wet, lifting, etc is just easier on good 100% cotton paper of 140lb or more, I like cold press or rough textures.
Brushes
I like Escoda Perla brushes, synthetic, great point, resilient and not too expensive, excellent work horses. These don't hold too much water, you need something like a squirrel mop for that (can be synthetic squirrel, they have those too).
Control of water
How wet to get the paper? When to stop layering and just let it dry?
Paint consistency
How diluted or heavy the paint should be to achieve a certain effect? There's an analogy for this, from tea to butter. An important thing to consider to avoid "blooms" or "cauliflowers" is to paint thicker over leaner, sort of like oil paint (fat over lean).
Mix on the paper
To me, this is what makes watercolor unique and beautiful, the effect of mingling pigments in the water is something no other medium offers.
Learn your pigments
In watercolor the unique properties of pigments matter more (more than oil or acrylic in my opinion). Play with your paints and identify which granulate, which are staining (these are very difficult to lift), which are transparent or semi-transparent.
Techniques and resources
There is a lot of content online, specially on youtube, not all is very good. I like these channels:
- In Liquid Color:
https://www.youtube.com/channel/UCnh5k3c1miCbQlt0Q8iXePw. She has this series where she showcases different paints and pigments, it's quite informative.
- Roland Lee
https://www.youtube.com/channel/UCblyGievHpud0hVZXyb71Cg his demos are good and I specially like his emphasis on negative painting, which watercolours lend themselves to
- Teoh Yi Chie
https://www.youtube.com/user/teohyc - Reviews of watercolour stuff, demos. Focused on urban sketching
Happy painting!