The recommendations to learn a lot more first are very reasonable, as you’ll build up skills, tools, ideas, and run into situations where you’re not satisfied with the way they’re doing something, so you start working on how to modify it.
But I wouldn’t discourage someone (who’s eager to be creative) merely out of fear that they might be duplicating efforts. You’ll learn during the process of trying to create, even when you fail, and even if what you end up with is later discovered to already exist somewhere. Merely having gone through the creative process will be a learning experience and hopefully a fun adventure. This is coming from a beginning magician but a long-time creator. Learn and create at the same time; don’t make one wait for the other.
I think that those with a creative urge should start creating from the very start. Work from both directions at the same time: study more, as others here urge, but work on creating – not just tricks, but gaffs, and play with them, and see what occurs to you.
There are lots of ways to get creative juices flow. Imagine a story of a princess, her suitors and the king, then try to apply card manipulation to illustrate it. Or take a card manipulation skill and think of what you could DO with it – flap cards + Halloween: vampire in coffin. Flap card opens coffin, revealing Vladimir…make him levitate, perhaps hinging forward to rise, unnaturally. Get some pale cards, like ones that fade from top down, and have normal jacks and queens first turn pale, their blood drained, and then completely white, so after he appears atop each, it changes, turning pale …then white… or even to a skeleton card.
Take Spell Purple. End with a purple card which is actually a flap card hiding another color (which continued spelling takes you to, and take it a step further with a double flap card.
Take a monte cristo packet and turn them all into royal scions whose parents gave them such long names that nobody could remember them (and the neighboring realms mocked them), so then they decided to rename them with numbers, just one, two, three, and so on… but that still left confusion, so they decided to rename them all ‘Prince(ss) Three’ (and you reaveal the force corner, invent a little denoument…
Take gimmicks and modify them. A cheap shell that appears to contain a deck but which, reversed, makes the deck vanish, can be modded to use your own box type and sample cards (one can be a prediction); or instead of vanishing the cards shrink; turn it over and you have a mini-deck inside matching in style; then do a trick with that with the same signed card on top, and have that end up matching a later chosen card… from the original deck which you then unvanish from the box. Or have the mini deck hiding a diabolical secret, a micro-deck tucked into a secret compartment you cut into some of the middle cards. The possibilities of what to do with that are numerous.
Take Out To Lunch and run with it… now, there’s a trick ready for creative twists!
Create by stringing tricks together so that they each share something and it all comes back to the original in a circle.
Create by taking a packet trick that originally proliferated 9 cards, one of which was an AS, to all AS, then modify it, by R&Sing it into just 3 original cards. Along the way, instead of just changing value, they also surprisingly multiply.
Maybe my suggestions are childish ones because I'm just beginning, but I'm not going to let fear of that stop me. One can also find creative ways to fail (humorously), as part of the entertainment. Want a deck jumbled face up and down for a trick? Accidentally drop it while shuffling in mid air, cards go flying everywhere, and you ask everyone to help just put it back together helter skelter...
Remember the rule of brainstorming: come up with as many ideas as you can without critiquing them at all. Both good and bad ideas get put down on paper and then you work from there. Ideas flow more smoothly if you can turn off that subconscious fear of putting out a bad suggestion or something unworkable. And it may be that in suggesting something unworkable and figuring out how to make it really work that you end up doing your real creation.
Don't be afraid to break it.
The recommendations to learn a lot more first are valuable, but don’t let it get in your way of trying to be creative from the very start. You may discover things by accident that you can use to create a new trick or plot