I HAVEN'T been gigging with ableton for 10 years, BUT, Ill weight in my two cents.
Investing in Ableton is a good idea in my opinion, its very versatile in terms of live performance and controllerism. If i understand you correctly, what youre trying to do, is pretty much just that. I dont think FL studio is quite as well equipped for live performance as ableton, or at the very least, not as user freindly.
I would also suggest that you plan out your sets in some manner. Im not saying prearrange the whole thing beforehand, but perhaps choose the samples and synths you'd like to use, keep in mind some compelling melodies you'd like and mix it in a manner that sounds pleasing so that it sounds good when you go up on stage. In my mind, the more prep and practice you do, the better its going to sound in the end.
as for the equipment, you have everything you need to do a live show already. Any further equipment would complicate your setup. while thats fine, you should learn what you have and be comfortable with your setup and workflow before buying new equipment that may not even fit with your style of live performance.