Two ways you can think about this.
You can forget learning any other flourishes besides Genesis. Volume 1 by itself has enough content to show your spectators that you've got finesse and skill. From your post, if you're that much into magic, spend your time and resources on your card tricks. After all, for a card magic person, $35 could have gotten you a pretty good magic book.
On the other hand, I agree with the general rule of not practicing magic routines or sleights in public. But I'm in the habit of carrying a deck of cards around. So when I have down time in a place that's not appropriate to work on my GOAT Change or my classic pass or my VCR Change, I play with flourishes. That being the case, don't purchase anything else flourish oriented. There's enough free awesome material to work on off of youtube. As you grow, if you're like me, you'll have seasons where you'll focus on working on a certain sleight alternating with seasons of learning flourishes. Maybe even subconsciously performing flourishes while reading a magic book...
Then there's the other option of getting Dan and Dave's Tricks DVD where their style is a seamless blend of flourishes and tricks...
Something to think about.
