For good equipment buy at a dive shop where you can try facemasks on. If you're buying for 1-time or rare use, buy the blister-packed stuff at Costco.
Mask: For a quality mask you need to try themonbecause different faces have different fit requirements.
Fins: Only fins I ever use (rarely) are for use in surf,because I used to be a lifeguard on the beach, so Istill have my "blue duck feet" fins from that. But for most non-athlete people, they'd be too stiff & cause leg cramps. Stiffer = more powerful but you have to be in good musscle condition. More flexible =easierbut less powerful. Whatever, make sure you get fins that FLOAT.
Snorkle: I hate those fancy snorkles with the flexible section between the tube & the mouthpiece. But that's just me because the only time I ever wear one is when diving to experience the magnificent beauty around the California Channel Islands. Diving in the giant kelp forests there is sort of like floating in a huge cathedral. Give me a cheap 100% stiff snorkle, that's always stabbing me in the face, which is a GOOD thing because that way you always know exactly where it is.
Summary: Forget shopping online. Visit a dive shop & pay a tad more to get their very worthwhile advice & custom fitting.