I used to be a derg, then a doggo, a catto, a leopard, a lynx, and then again a cat is what I am now!
As it's already been covered by above friendly furs and scalies, it may shift as your heart goes, and it's never a bad thing!
Pure aesthetics can ring it, or spiritual connection can also make the job done! And it's even more stable when both are satisfied. I'm both, by the way!
Initially the aesthetics, later the connection, and then the lore setup stuff gradually came after over time.
As you've been suggested by above people, feel free to take a look at how others established their sonas!
After all, you'll need some research yourself if you're wiling to keep your personal traits personal(because then, people can't give you precise guides to ultimate). But hey it's always your call there!
Take your time looking back on yourself, do research for those species you see fit; or simply pick/make any you feel like straight away and leave else to your heart and time! Either way, what's important is that your sona is to your content!
Good luck on your sona build, herman568!