To make a good arrangement, you need a good vase and beautiful flowers.
You had better look
for vases with natural surface and texture, like baskets of wild vines,
unglazed potteries, etc.
First of all, think about where you will ultimately place your arrangement,
then decide the size and the style of the piece, for example, viewing from
one side only or in-the-round.
Next, choose flowers, thinking about the color harmony. Keeping your
original plan in mind, let yourself go and freely design the arrangement.
Soon, you will have something in front of you that is truly special.
Then try again.