My first, and strongest recommendation, is to read everything you can get your hands on. Yes - read. Videos are decent for learning what a move or trick looks like, but otherwise they are horribly inefficient ways to convey information. Further, the information that's important to the act of creating magic is almost never conveyed in videos. You need to read - preferably older books as much as possible. The contemporary offerings are largely just rehashes of old books.
The reason I recommend this two fold. First, after you spend some serious time reading books, you'll have a vast amount of knowledge and a library to reference to check for existing methods. Second, you'll realize that it's incredibly difficult to come up with something truly unique any more.
This is not to discourage you from trying to create, but rather to give you a heads up that for some time everything you think of will likely have been thought of already. It happens to everyone - I know I have accidentally recreated at least a half dozen routines, some of which I thought were really out there.
While developing that wealth of knowledge I also recommend exploring other subjects. Whatever is interesting to you. It's critical that you not just obsess over magic. Wayne Houchin, in an interview from several years ago, mentioned that his magic didn't get "good" until he stopped obsessing over magic and started focusing on having other experiences. This is because most people can't relate to magic, and for a performance to be interesting and engaging, it has to be relatable. So having a variety of experiences to draw from to create scripting and material will ultimately do far more for you than any particular sleight will.
Once you have that wealth of knowledge and experience, all you need to do is use it to create things.
Now - coming up with what to create - or "being creative"- is a skill. A lot of people claim it's something you're either born with or not but that's not true. Creativity can be developed just like any other skill. The way to do that is to be creative. There's a few ways you can do that -
1) Look a trailer for a trick that you think is interesting. Try to come up with 6 methods to accomplish it. Don't worry too much about them being viable methods, just let your brain do its thing. Once you've come up with 6 distinct methods, that's when you look at them critically and toss out anything that is clearly not going to work practically. Then pick one, and try to make it happen. Doesn't matter if you never do that trick or method for real, just see if you can make it happen.
2) Think about something that would be cool to experience. I usually look at "unsolved mystery" kind of stories for inspiration in this regard, or mythology/legends. When you've got something that seems cool, do the 6 method thing above.
3) Examine older routines and look for weaknesses or things you would prefer to change. For example Aaron Fisher took the two-handed pop out move and wanted to be able to do it with one hand. So he just sat down with a deck and went through it beat by beat to figure out exactly how, mechanically, to make it happen. Tommy Wonder did the same thing for his version of cups and balls. Essentially this is a process of identifying a problem and fixing it.
Personally I'm thoroughly against the idea of creating tricks or methods just for the sake of creating something "new". I find this process tends to end with methods and tricks that are not practical in real world scenarios and that's the only way I perform (no virtual for me). This is also a big reason the market is so flooded currently.
So! There you go. Good luck!