The only gimmicks you should own in my opinion are ones that wont be a hassle to carry around with you.
Unless you need some big heavy hitters for a show you're planing to do, a few great every day gimmicks are
Odyssey (100% recommend if you're into ring magic, its not just hype)
Loops (These are a must have, you can buy the cheap asian ones off amazon or get yigal's)
The raven (If you can fit a coin vanish into you're routine, i find its a decent opener since its awkward to get ready)
An invisible deck (Just stick one in your bag as a backup trick)
Departure (Ive found its a bit loud but if that doesnt bug you its so easy to setup and carry with you)
Rising card (Depending on which gimmick you build or buy it just fits in with the rest of you're cards)
The raven is the only one out of these that is somewhat of a hassle to carry, however they're all very effective gimmicks that wont be a bother to have on you, thats why i would consider them "Must haves"