Reddit mentions of Princeton Artist Brush Neptune, Brushes for Watercolor Series 4750, Quill Synthetic Squirrel, Size 6

I think it depends on her age / level of knowledge about painting; can she be responsible with tube paints, for instance?


The Cotman set mentioned already would be a good bet, it's once of the nicer student grade paints. Just a warning that you can get it on Amazon for significantly cheaper than michaels / hobby lobby etc. Just search for Cotman - theres several different styles (tiny travel size, bigger pans, etc).


My recommendation however if she is as you say not quite a beginner, and can be responsible with tube colors, would be to get her some artist quality paints. These are expensive to jump into; about $10-12 per tube of paint. However, each tube should last her a very long time. You'll also want to get her a palette of sorts to put them in, she'll squeeze out paint to the wells and allow them to dry, that way all the colors are easy to access. Watercolors can be reactivated with a dab of water.


There are many brands, but I love Daniel Smith, M. Graham, and Holbein. You'll want to buy these from dickblick.com, cheapjoes.com, or jerrysartarama.com - these places are a few dollars cheaper per tube and that really adds up over time. The exception is usually 'sets' - some brands sell sets of paints that compliment each other, and these seem to be cheaper on amazon.



As for what colors you should grab if you choose to buy tubes, there are A LOT, you'll at least want to get the basic colors that will allow her to mix most other colors. This however can be a really personal choice (what colors you want in your palette) All Daniel Smith unless stated otherwise:


Essential shades:

• Hansa Yellow Medium
  
• Quinacridone Gold
  
• Carmine
  
• Ultramarine
  
• Phthalo Green
  
• Burnt Sienna
  
  
  Nice to have:
  
  
  
• Moonglow
  
• Quinacridone Rose
  
• Naphthol Red (M. Graham)
  
• Azo Yellow (M. Graham)
  
• Undersea Green
  
  
  M. Graham has some really nice sets:
  
  
  https://www.amazon.com/s/ref=a9_asi_1?rh=i%3Aaps%2Ck%3Am.+graham&keywords=m.+graham&ie=UTF8&qid=1483228508
  
  
  Have a look here to see what she could mix with the essential shades only:
  
  
  http://janeblundellart.blogspot.com/2014/06/just-6-colours-lovely-limited-palette.html
  
  
  She may feel really limited if she's not sure how to mix colors yet.
  
  
  And so she has somewhere to put them:
  
  
  https://www.amazon.com/Martin-Mijello-Airtight-Watercolor-18-Well/dp/B002664868/ref=pd_bxgy_201_2?_encoding=UTF8&pd_rd_i=B002664868&pd_rd_r=KGKTV5R413WMN7JM49ED&pd_rd_w=27A37&pd_rd_wg=coxt7&psc=1&refRID=KGKTV5R413WMN7JM49ED
  
  
  
  And, incase you wanted to get her a whole "Artist Quality" set to get going with, maybe grab some paper:
  
  
  http://www.dickblick.com/products/fabriano-artistico-extra-white-watercolor-blocks/
  
  
  (I'd recommend cold press, and whatever size she tends to like to paint at - 9x12 feels not too big, not too small to me, personally)
  
  
  Brush recommendations:
  
  
  https://www.amazon.com/gp/product/B00512C1VS/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
  
  
  https://www.amazon.com/gp/product/B004BN7R9E/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
  
  
  https://www.amazon.com/gp/product/B00409JAEY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
  
  
  http://www.dickblick.com/products/escoda-versatil-brushes/

$100 will get you pretty far! obligatory ymmv, a lot of supplies depend on what and how you paint (do you paint large or small? do you paint outside a lot and need a travel kit? and so on), etc, etc, but here is how i would spend the money:

• paints
  
  kuretake gansai tanbi, 36 color set - the best set of watercolors i have used and relatively cheap, the colors are vibrant, mix well, and set beautifully.
  
  
  
• paper
  
  probably where most of the money should go after upgrading your paints. i like the strathmore 500 series and the canson papers for sketching and learning. other higher end brands that are recommended a lot are arches, bee paper, and fluid 100. definitely try out both hot press and cold press, people usually develop a preference but one is not necessarily better than the other.
  
  
• brushes
  
  honestly, brushes are not that important as long as they are not frayed or shedding. i've seen tons of professionals use and recommend this cheap set by grace art. i also like the princeton neptune brushes.
  
  
• extras
  
  if you still have money left, i would suggest trying something cool like metallic and pearlescent paints if it interests you. or use the money towards other mediums if you want to branch out.