Comes down to one simple question, how durable do you want this to be? The durability of the item is relative to both cost and time needed to put it together. If this is something you're only going to use once then something cheap will be fine. For repeated use, then something more expensive.
But either way you'll need a good strong base to start from in which I'd suggest crafting the handle first along with it's electronics system. From there build around it creating the cannon.
Do you already have an idea of how you plan to build the cannon? Also do you require instruction for the LED wiring?
When in doubt, just take the next small step.
With that next step take a deep breath. It calms the mind.
When the mind is calm you realize the best is still yet to come.