I’d stay with rolls if you aren’t familiar. And if they have a light soy sauce, try that at first. Isn’t quite as strong. If you like spicy, then mix some wasabi into the soy.
For beginner friendly rolls: Anything fried. Just go with ingredients you like. Shrimp Tempura is usually a safe bet.
If you’d like to try something raw, Tuna and Yellowtail are great, if the cut/quality is good. They’re clean and simple, just seaweed, rice and fish. If you like this, in time you’ll probably start to enjoy sashimi. If you don’t, no point in getting sashimi. If you’re in the middle, then give it time. It’ll probably grow on you.
You could also try eel. It’s not nearly as odd as you might think going in, and it’s typically cooked. Some places do their eel up too sweet for me, but it’s usually pretty good.