I can't cartwheel or handspring whatsoever. I don't quite yet have the strength, and I super-definitely don't yet have the balance. So I always work on split grips from the top down, going into a split grip straightedge from a standard invert, then drop it to one side into jacknife, then swing one leg around into an aysha. It's not super pretty yet, but it's helping me find the balance point for my SG aysha and split grip. Which will in turn help with the handspring.
But I am a weird freak like SissyBuns who got SG aysha before elbow or forearm grip, neither of which I can do yet, literally at all. But, I've always had a knack for the flag and its varieties, so I'm working on my flag invert because I know that grip will get me up and over in basically a forearm grip. For me, learning a new move that really challenges me is about transitioning into and out of it in ways which most take advantage of my personal strengths, then modify the move to make that strength more well-rounded and add new components to it. For example, when I learned SM the standard double cup grip was easiest and took advantage of my strong biceps. But then once I learned that I started working on grip variations, and my SM is better overall because of the new control I learned from each new grip and thus using different muscle groups to execute the same move.
That said, if you can't do aysha or straightedge, think about the horrifying backwards fall that could result out of trying a jacknife before you're ready and at least use a spotter and a mat or at most reconsider and spend a while working up to it. Of everything I can do in split grip, jacknife is probably the one I'm still least comfortable with, and I work on my split grip literally every heavy practice. (which has only been a little over a month, but still) One thing is for sure, I've never done it from a butterfly, but I'm definitely going to give that a try now.