It's been said that there are no new ideas.
Creating magic is a skill just like any other talent in magic. Some people are just naturally born with the gift of creativity (Blake Vogt) and others have to practice constantly at it until they learn all the nooks and crannies of making something that's marketable. Also, sometimes creativity can't be forced. It can sometimes occur entirely by accident or out of necessity.
An example would be when I was first starting out in magic. My second performance ever in front of an audience of random people was at a local food pantry a mentor friend of mine would take me to. I was going to use a coin through hand effect that I learned from Howcast on YouTube as my opener to tell a story. Unfortunately I hadn't taken my angles into consideration and everyone saw the hidden coin tucked away in the pockets of my fingers. It was completely humiliating and I had to recover fast in order to save the rest of the show. I really liked the coin through hand plot though and was wondering if there was anyway I could do it with my hands being clean and the beginning and end of the effect and I also wanted it to land in the spectators hands so I could get them involved. I searched and didn't find anything that met my requirements so I began developing my own routine through trial and error. Eventually I came up with a method that I really liked and published my first effect, Doubting Thomas, on penguinmagic.com. Even to this day I still use the principle of the routine in my stage and parlour routines and I'm even working on an update to the project in the form of a version 1.2 of it.
Another instance of creating magic was when I was alone in my apartment I would just randomly mess around with objects I found lying around. I drink a lot of water so I had a lot of water bottles to play around with. I thought it would be really cool if I could just crush one as flat as a pancake. I knew of Eric Ross's Crush but it was no longer on the market and I heard the gimmicked method was not always reliable and the ungimmicked method was not practical for real live performance situations. So through trial and error I came up with my second release which I published on the Marketplace here called No Pressure. Not too long after I published that effect, I was at a party in Detroit with no magic items on me whatsoever. I was put on the spot to prove that I was a magician so I just winged up a 100% impromptu handling of No Pressure. I was literally forced to expand upon a creation on the spot but in the end it worked out beautifully and I'm very proud of the entire No Pressure project.
Right now I'm still active in creating. I have two effects that I feel very good about but I'm being very careful about releasing them. I want to make sure they are not only practical to me but to other performance styles as well which makes for an interesting creative challenge. I also am doing a lot of research into the originality of the effects. One of my creations in particular I'm very proud of and will use to compete in talent competitions. It has all the check marks for me: 100% impromptu, uses borrowed objects, borrowed object is altered and can be kept by spectator as a souvenir, and is useful on stage as well as street magic.
My last piece of advice is don't be afraid to throw out some ideas or sit on them for sometime. Some of my old ideas are complete trash and I laugh at myself for ever thinking they were practical for real performances. Other ideas I'm just sitting on waiting for that right thing to click in my mind, that "Aha!" moment. Through researching other effects for originality and just messing up sometimes and not being afraid of failure, I'm sure you will land on something cool. I struggled for months on one of the effects I listed above on a particular move until I was running a practice trial on a magic club I belong to. They were doing something odd during the performance because they thought it was a method I was using and they were trying to throw me off and little did they know that they actually helped solve an issue by doing that. It was completely random but it made the whole thing come together.
Don't give up! Just try to create at least one-two new effects a week, even if it isn't original or usable. It will help train your brain to think more abstractly and to solve problems more critically. You will only get better with practice. Best of luck!