These ones I did freehand, you can see they are a little wonky but I'm not unhappy with that look.
You can see my tutorial about drawing more symmetrical mandalas
here if you want some more ideas.
Next I simple cut them out and glued them onto card blanks.
Next I tried a more rectangular shape of felt pen 'watercolour' and drew feathers on top.
I added the greetings with stamps.
There are no step by step photos here but they are done in exactly the same as the mandala ones. Scribble with the water soluble felt pens, wet with the paint brush and then leave to dry completely.
Then doodle whatever you fancy. I did feathers filled with doodle but I'm thinking they could easily be tweaked into leaves.
The colours don't blend quite perfectly but I love that you can get this effect with something as simple as a kids felt pen or two.
I do have some bits and pieces of actual water colour and some water soluble colouring pencils that I had as a teenager (never throw anything away that might be useful!) so I'm going to do some more experimenting soon.
There are millions of ideas online for zentagling and doodling (I have
a board on pinterest if you want some more inspiration). If you are not feeling very artistic then you could use stamps, but honestly the doodling doesn't have to be complicated to look pretty. It's all about overall effect rather than expert drawing - have fun!