Yeah it depends a lot on your art stye! I also have a portal in my comic, and I've kind of improved at drawing it during the course of this chapter
This is the first time it appears:

And this is the last time I drew it (page not published yet tho)
Started using white lineart instead of gray, and it make it look more glowing, and made the center more like a bright core, which I also think works better.
You can also look and reference shows that have portals. Lion in Steven Universe comes to mind, but I'm sure there are plenty of other examples as well. Take some screenshots and see how different artists/IPs have solved this problem! 