In my lifetime, I have painted with darned near everything meant to be used as paint. I've used automotive lacquer, industrial enamel, vinyl paint, fabric ink, dye, water colour, gouache, pastel, acrylic and oil - and probably a few I've forgotten about.
These days I paint exclusively in oils but they do have the issue of the foul aroma and messy clean up with turpentine so it's understandable why a lot of people don't begin their art journey with oil paint.
A lot of beginners do seem to start out with water colour and I've never really understood why. Other than the ease of cleaning up, since water colour remains water-soluble so will always wash out of brushes, I'm not certain why it enjoys such mass appeal to people starting out. Water colour washes are transparent so once a mistake occurs, it's virtually impossible to fix as it continues to show through subsequent layers. Even after decades of using all manner of media, I shy away from water colour as it requires an organised approach for the best results. It actually adds a level of difficulty that beginners don't need.
Gouache is basically water colour with chalk added. It shares the benefit of easy-clean-up but because it is far more opaque, it is somewhat more forgiving than water colour. However, because it always remains water soluble, heavy handed attempts to re-work existing layers of paint can soon lead to "mud". Still, I'm tempted to give gouache a serious go one of these days.
In my opinion, acrylic paints are among the best media for beginners. There is a range of opaque and translucent colours and they wash up with water but dry waterproof. There is a huge range of additives which will extend the qualities of acrylic paints. There are thickeners that allow for heavy impasto work, reducers that add water-colour-like qualities, retarders to slow the drying time, crackle mediums to make instant "ancient" paintings and more.
So when I first started in fine art, acrylic was my medium of choice. I'd used hundreds of litres of the stuff as a muralist and signwriter so I had a firm grip on its strengths and weaknesses, including the fact that a lot of colours will dry significantly darker than you might expect.
Acrylic paints certainly aren't without their problems and the worst one will bite every acrylic painter one day. The fast drying time, combined with acrylic's waterproof quality, means that your brushes are in constant peril. If you put a brush down with paint on it - and forget about it - then that brush might well be destined for the bin. There are cleaning products that will help recover such a brush (methylated spirits will do it if you catch the problem early enough) but it will never be the same.
IMPORTANT: Sable brushes and acrylic paint should never share the same space unless you're meticulously organised, or rich. I'd recommend some of the vast range of synthetic brushes for most acrylic work.
In my experience brushes have to be regularly flushed in a large jar of water while painting and thoroughly cleaned with soapy cold water (not warm or hot) when finished.
For the plein air (outdoor) artist, acrylics pose another problem. Any slight breeze, especially on a warm day, will constantly dry the paint on the palette. It's a genuine frustration on the worst days as it starts to feel like you're painting with clay, or sand.
To get around this problem, I made myself a non-drying palette. This is very simple and worked better than I'd anticipated.
I used a clear plastic kitchen container about 25-30cm square and 5-7cm deep. I cut a chamois-like dish cloth (the soft, slightly-furry kind) to fit the bottom of the tray and a sheet of grease-proof (baking) paper to sit on top of this.
I carried water in a large bottle and added a little to the tray before starting to paint. The trick is to get the cloth just wet enough that no water is slopping around. Then I'd set out my colours on the baking paper. The sides of the container help to reduce the effects of a light breeze and the wet cloth keeps the paper palette cool and moist. If things got too messy, I'd tear off a new sheet of paper (I carried a small roll with me) and lay it over the top and keep painting. On very hot days, a spray bottle is a handy addition to help prevent the whole thing drying out.
When I was finished, I'd pop the lid on the container and the paint would still be useable when I got home. The paper palette is disposed of and the cloth rinsed out and dried for next time.
IMPORTANT: Don't leave the wet cloth stored in the sealed container. I learned that rule the hard way - it isn't pretty!
I used jar colours, rather than tube colours because, at the time, they represented much better value. The problem is that it's easy for things to get messy if you work directly from the jars. One day you're going to dip the blue brush into the yellow jar then kick yourself silly. Also, every time you open the jar, you expose the paint to fresh air and I've found that the paint can thicken over time and there is always an annoying buildup of dried paint on the jar thread - and it seems to like jumping into the jar at every oppoortunity.
To solve this problem, I purchased a couple of dozen small squeeze bottles. I scooped colours into separate bottles with popsticks then resealed the jars. I even made some pre-mixed colours which was often a great time saver. Old film canisters offer an alternative (if you can find them these days). They weren't quite as handy as the squeeze bottles but were excellent if I wanted to use large washes as I could add a retarder medium and water to the container and use them almost like ink.
I haven't used these bottles for years but many still have perfectly useable paint in them. Of course, if you're using tubes, a lot of these problems are already solved for you. My only suggestion there would be to squeeze the tube before putting the lid back on to minimise the amount of air inside.
In my early days, I painted exclusively on quality canvas boards. They made life easy. These days it seems like every second shop is selling either canvas boards or stretched canvases for next to nothing. It would be hard to beat them for learning with.
So there's my thoughts on acrylic paint, the perfect beginner's medium - well, it was until they invented water-mixable oils... :)