How can I improve on this picture? (critique)ff

First of all shoot RAW so you can compensate exposure in PP; also you have a better control over sharpness and balance

Try different angle, the background is not great, especially the big contrast between green and black

For JPG try some PP with masks, like this ( hope you don't mind I used your shot):

I have just increased ( exagerated) the colors on the flower and the brightness and contrast on the background.

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Light is my friend, time is my enemy.