Watercolor Brushes
Princeton Neptune
To get started, this Neptune set is all you really need and is very affordable. It has 4 different brushes that cover pretty much all the basics needed to paint botanical and landscapes or portraits. If your style is more detailed, you could add the elite set to bring in less wet brushes with thinner tips. I have both.
Princeton’s synthetic squirrel brushes are high-quality brushes designed to surpass their natural counterparts.
Princeton’s Neptune™ brushes hold colour excellently and come in a large range of shapes, including mottlers and quills. Neptune squirrel brushes have traditional solid wood and sea glass aquarelle handles. Shop sets here
Also a nice Neptune Watercolor brush set here with more rounds on Amazon here
Professional Brushes:
For those looking to upgrade to a professional watercolor brush, my all time favorite brush is the Escoda Versatil 1549. I have this in all sizes and when it comes to botanicals, this brush can't be second guessed. The long round hairs with defined point put this rigger style brush above all with a large belly that holds plenty of paint and water and a gorgeous smooth flow on paper. I never get tired of reaching for this brush. It's still my all time favorite and worth every penny spent on it.
VERSATIL is the perfect synthetic alternative to Kolinsky sable. Designed with versatility as its main feature, VERSATIL really lives up to its name with exceptional snap, superior absorption and fluid retention. It is excellent for use with both watercolour and oil/acrylic, allowing artists to create fine details as well as providing superior performance for colouring larger areas and background. VERSATIL is an exciting new addition to the synthetic brush world.
If you have to choose one I would go with the size 10, then for those a bit more timid try the size 6, it's a great way to start.. I can make beautiful leaves and thin lines with my 10 but a beginner may need to hang in there until you get the feel of this professional brush..
For even thinner lines without having to adjust the hand and technique they have a 0 and 4.. which won't do thicker lines or larger leaves in one stroke but will give you consistent thin stems and straight lines even if your hand is a little unsteady.