my front spoiler keeps clipping off, do I need it on my car? if so how can I get it to stay on?

The front spoiler, commonly known as a splitter is here for aerodynamic purposes as well as aesthetic purposes. on a car like a fiesta they aren't very necessary so if you tok it off the only affect it might have is a slight and I mean very slight decrease in your fuel economy. 

Tiger seal is good for this sort of stuff, the clips will just keep breaking. Just make sure the area is well clean and no wax left on the bodywork you're bonding too.

Or like you say just remove it (surely it's not that much of a banger to just leave body panels off though lol). As long as there's no sharp edges you can do what you want with the bumper. As said above, it's purely aesthetic.