Moving into intermediate

I’ve been a novice for almost 10 years.. did my first sprint at 16 in 2016. Best time was performed in 2019 when I was a d3 student athlete in swimming. Took some years off. Spent last summer getting back into shape, fell back in love, and went within 5 minutes of my best time (2019). Training towards olympic distance. Looking for recommendations for biking shoes/helmet. Really out of my element I’ve mostly been running and swimming my whole life but I really want to commit. My dad said I need to make sure I buy biking shoes that “fit” the road bike my mom lent me… do any 3 bolt cycling shoes work? What do I need to do to narrow down? Can I buy any “road bike helmet” if I were to search Amazon?