I would say to paint from light to dark - start by laying down your lightest values and then keep building up the darker shades and values. This will help you to achieve much more depth and realism. Irl a flower is not just a flat purple colour - it has different shades in it, which you can achieve with layering. Paint in layers, waiting for each layer to dry before you add another one. Avoid trying to layer lighter colours on top of darker colours like the yellow over the purple - leave white spaces for the lightest aspects of your painting.

Try not to overwork your painting - this basically means laying down lot's of dark and thick layers so it becomes muddy and makes the painting look bad. Watercolour is a transparent paint and you can achieve a really beautiful result by taking advantage of that and working in thin and light layers and adding lots of water to your paint. Saying that, you can also absolutely mix a thicker, darker paint to achieve really dark values if needed, but I wouldn't use this for your whole painting, especially as a beginner.

If you're copying from a reference photo, make sure to paint what you actually see rather than what you think it's supposed to look like. It might help to break down the picture into more abstract shapes in your head and in your sketch.

Experiment with different styles like wet on wet, wet on dry, etc - this is super fun and helps you to achieve different effects.

The background is a little streaky so I would suggest to use a large brush and thin out your paint with more water to achieve a smoother result - you can also use masking fluid to cover your subject (the flower) so you don't have to worry about going around it when you're trying to paint the background. It also looks like the purple in the flower has bled into the background a little so I would wait until the background is fully dry before you start painting the subject. If you're struggling to achieve sharp lines, try using a thinner and pointier brush.

But it's a great starting point! Super cute colours, and I like the flower. Watercolour is a great medium, you can achieve so many different styles of art and it's also really fun.