It's probably easiest if you pick a focus fabric first that has the colors you want - for instance a busy print with lots of color. Then you can pick fabrics in some of the other colors in the focus fabric. Each fabric doesn't have to match each other or have all the same colors, but it looks good if they kind of blend together as a whole.
For example, if you found a busy floral with purple/lavender, pink, yellow, green, you could then look for other prints that have some of the colors in them. Like maybe a print with yellow and pink, or green and purple. Vary the size of the prints, larger flowers, smaller flowers, leaves, scrolls, etc. You can get ideas by looking at the collections by some of the manufacturers. You can mix and match. I hardly ever make anything exclusively using one collection.
Hope this helps! :)