Before you start painting it is useful to consider the different paint types and the characteristics of each. If you are complete beginner, here is a summary of each type of paint and their key features:
Watercolour
Watercolour is a challenging medium for beginners but that shouldn’t put you off trying it. If you make a mistake in watercolour, it usually means starting a new painting unlike other mediums such as oil and acrylic where you can paint over the paint underneath and make adjustments.
Watercolour is used in watery ‘washes’ traditionally with lots of water and the white of the paper is used to shine through for highlights and lighter areas. Paper is very important for watercolour, you need a good quality watercolour paper for the best results. A natural fibre brush is best that can hold some water for washes. Traditionally watercolour is used in washes that ‘bleed’ into one another and it is supposed to be a fluid and spontaneous medium.
Acrylics
Acrylics are suitable for beginners because they are forgiving in that they can be layered and adjustments can be made. They are also water based and easy to use in general. They are used fairly thickly and the finished paintings will look opaque in nature. The challenge with acrylics is their fast drying qualities, they tend to dry quickly so blending can be challenging. It can also be difficult not to make them look flat. Layering acrylic will make your work look a bit richer than used just in one layer. Acrylics are good for detail, you can create sharp and detailed lines and edges with them.
Oils
The main characteristic of oils, is that they are oily! This means they can be blended very well, they have a lovely buttery texture and you can manipulate the paint for some time before it dries. This makes oils good for making adjustments and layering paint. Oils are a slightly more difficult for complete beginners because of the oil based nature, this means you have to use other mediums other than water to dilute them. Oil based oils will need to be diluted with a solvent like turps or white spirit or non solvents can be used such as linseed oil or zest. However these days there are water-based oils which have the same qualities of the oil-based oils but you can use water to dilute them and clean the brushes.
This is a very quick guide to each paint type, for more information look at my posts What are Oils? What is Watercolour? and What are Acrylics?
rebeccaarttutor.com 
Water-based oils – that just sounds wrong.
I’ve only ever used watercolour from the start of 2018 but it wasn’t an informed decision as such, I didn’t know about acrylic at the time and thought that the natural progression of things was that watercolour was for beginners and oils for more experienced or professional artists. Anyone reading this that’s just starting out – my previous point of view there couldn’t be more incorrect !!
Good point stevekiddart, the general ideas is that watercolour and acrylic are the best places to start but I don’t agree with that idea in terms of watercolour. Personally I find watercolour a tricky medium for beginners. I say just go for what you would like to try, acrylics are probably the easiest for beginners but if you want to use oils, go for it! Yes ‘water-based oils’ does sound odd, but in my opinion they are great, being able to use water instead of linseed oil, zest or turps makes life easier and they are in my view just as good!