First check your local legislation, that'll give you a starting point. In my country helmets, lights AND reflectors are required by law for urban riding.

I'd start with platform pedals and regular shoes, as you ride more you can decide wether you want to go clipless or not.

Gloves help a lot not only in case of crashing but the padding is comfy during long rides, IMHO.

Essentials for fixing an unexpected issue: a multitool (allen keys and chain tool), spare tube (or patches), mini pump. You can carry these in a jersey pocket or a dedicated saddle bag (or backpack if you're commuting with one).

I think these are the essentials for starting. As you ride more you'll start noticing your needs and riding style and can add things accordingly, such as a water bottle, cycling computer, cycling kit, a rear rack and bags, etc.