If you are just starting out at the pattern-mixing trend, floral and stripes are a perfect pace to begin.
It's a fun combination that doesn't require much thought. Pair your favorite striped top with a super-trendy and available-everywhere-right-now floral bottom (my favorite on sale here).
Just make sure that the stripes are simple and that the color theme is slightly similar to one of the colors in the floral print. Blue/navy stripes are a safe bet but red would also be a good option.
And don't worry if this kind of floral print is too busy for you. Try an option like this (on sale) and the effect will be the same, just a little more mild.
What patterns are you mixing for spring?
Top: Old Navy (a spring alternative here)
Heels & blue bracelet and short necklace (similar options here): Forever 21
Long Necklace: J. Crew
Sparkly rose gold bracelet and watch: Charming Charlie