Being a self-proclaimed art supply hoarder and a passionate watercolor supply tester, I have came across probably all the hyped and underrated watercolor supplies in the past 5-6 years. Here are my take on where I think it makes sense to splurge or where you could definitely save some bucks without compromising the quality of your work.
SPLURGE - 3-4 watercolor brushes

If you are going to paint nature, animals or botanicals you would need three types of good quality watercolor brushes (natural or synthetic kolinsky sable or squirrel hair):
size 2 or 4 pointy round brush for fine details
- e.g. Silver Brush Black Velvet https://www.jacksonsart.com/silver-brush-black-velvet-squirrel-risslon-brush-series-3000s-round-size-2
size 8 or 10 round brush with less pointy tip for versatility
- e.g. Da Vinci Casaneo https://www.jacksonsart.com/da-vinci-casaneo-synthetic-watercolour-brush-series-5598-round-size-8
size 10 or 12 quill mop brush for background and washes
- e.g. from Windsor & Newton Pure Squirrel https://www.jacksonsart.com/winsor-newton-pure-squirrel-mop-brush-no-10
If you want to paint buildings or practice urban sketching, I would also invest in a good quality flat brush
- e.g Pro Arte Renaissance Sable 3/8 in flat brush https://www.jacksonsart.com/pro-arte-renaissance-flat-3-8
Side note: it does not mean, cheap brushes are not good! I am a huge fan of Art Secret which is a chinese brand selling mainly on Aliexpress and Temu. Their brushes shed a bit first but once you "broke them in", they are excellent!
SAVE - watercolor paint

You would think it is contra-productive... paint must be the most important, right? not at all! Actually it makes little difference if you are a hobbiist or just paint in your sketchbook whether you have super expensive or cheap paints. It only makes a difference when you sell originals. Cheap watercolor paints are often weak when it comes to lightfastness. In this case I would definitely stick to the well known brands like Daniel Smith or Schminke.
My two favorite cheap watercolor brands are Royal Talens Van Gogh Watercolors
and Paul Rubens Watercolors
Both are vibrant, not chalky at all and nicely transparent. The Van Gogh paints have all the usual info with pigment numbers, transparency and lightfastness while the Paul Rubens lack this kind of information.
Side note: unfortunately White Nights are not really available globally anymore - they are a Russian brand - but they used to be my third favorite cheap brand.
SPLURGE - watercolor paper

This is probably the most important art supply when it comes to watercolor painting. First of all, watercolor needs special type paper that can absorb water without disintegrating. It has to be at least 200 gsm (gram per square m). Don't try to use printer paper or sketchbooks that have thinner paper. You will struggle.
Secondly, and this is probably a rather unpopular opinion amongst many, buy 100% cotton watercolor paper! Even if you are just starting out and don't want to spend much on supplies. It makes a HUGE difference for washes, blending color and manipulating paint.
I have tried many-many different papers and these are my top 4 brands:
- BAOHONG - you can buy it on Amazon or Aliexpress/Temu. Medium price, excellent results
- Arches - many swear by it and for a good reason. Once I found a cheap Amazon seller on the German site, I never bought anything else.
- Fabriano - I had beautiful results with Fabriano Artistico papers but I must admit, I rarely buy it because of the price
- Paul Rubens - the cheapest of the list. I bought a bunch of different smaller sizes and I really liked them! Totally worth if you are starting out.
What I tried from the more expensive brands and I didn't find particularly good is Hahnemühle 100% cotton watercolor paper. I love their museum quality giclee papers but not their watercolor ones :(
SAVE - palettes, cups, special tapes, etc.
Everything what belongs to the "others" category. Not worth buying anything expensive. I have tried all types of palettes and I came back to the cheapest 2.5 EUR plastic ones. They are very easy to store and you can travel with it and after a couple of use the water-beading stops happening as well.
I use old empty glass jars, paper towels and either frog tape or cheap washi tapes. I use an old cutting board for taping my paper onto or I tape directly to my desk. I think desk easels are overrated and I find them inconvenient (I bought two, both are collecting dust :( on my shelf)
So use what you have at home or just buy a cheap version.
While I understand why people say that watercoloring is an expensive hobby, I think you can save a lot of money if you know where to splurge and where to save. I hope you can find something useful & if you got some good tips, share it in the comments :)