Reddit reviews Refun(TM) 2-pack of RED and White Silicone LED Waterproof Front and Rear Bicycle Light, 1 Red (Rear Light) and 1 White (Front Light) for Cycling Safety Flashlight

if you are going full rain-gear, it would include either making your only bike all-weather compatible (full fenders, etc) with the understanding that it will be clunkier to ride and will deteriorate more quickly (rust, sand, drive train, brakes). if you can swing it, get a beater bike that is specifically set up for rain and keep your nice bike (if your bike is nice) in fair weather condition.

 

carry a basic toolkit (spanner, hex wrench multi tool, spoke wrench, tire levers) and a spare tube or two. unless you want to carry a small handpump, you could invest in some CO2 cartridges and a small inflator. include some elastics, bungees, and a small roll of rubberized gaffer tape (just tear a strip of a few feet and roll it on itself so you have a little finger of black magic) -- the tape can be used for many things, from lashing something to your frame to layering up and booting a tire puncture. last but not least, buy a box of rubber gloves, and keep a few pairs rolled up in your kit. all of this can fit in a small saddlebag, handlebar bag, or hip pouch.

 

along with your standard toolkit and flat repair/replacement kit, carry an emergency rain poncho and a pair of rubber boot covers. boot covers are especially nice if you end up getting a pair of shoes that you don't want sprayed with water and sand should you get caught in a downpour or have to ride on sticky/tacky surfaces after a rain.

 

if there is a chance you are going to be riding at night, get a rear flasher and a good headlight (a powerful LED array with multiple modes & brightnesses). good lights usually have a rechargeable external battery pack -- carry a spare battery pack or at least get a few cheap LED flashers (frog knog or similar) to keep in your toolkit as a backup.

 

one last thing that i find helpful is keeping a few drawstring backpacks rolled up in my kits, as they can really come in handy if you need to pick up or carry something (or remove some clothing) unexpectedly. when not in use they fold up smaller than a deck of cards. if you have to lock your bike up outside and have a nice saddle, you can tie one of these over it so it's not so obviously nice.

 

i didn't really answer any if your big questions with specific recommendations, or cover any basic cycling equipment (like riding gloves or bike locks), but these are little tricks or lightbulb discoveries that i've picked up over biking in the city for the past 12 or 13 years. most of the small things are non-essential, but come in very handy and can save a lot of unneeded cleanup and frustration. now i never ride without them.

At 3 miles, you could walk that in 45 minutes, so 15-30 minutes to ride each way depending on the hill. Good that you are planning it now, instead of waiting till later. I think the first thing you need is a feasible route. Perhaps you already do, but it is more pleasant to ride without a car behind one. So perhaps you can ride much of it on roads that are less busy and likely have a lower speed limit. Google Maps has a bicycle option so you could see what that suggests. When you get your bike (or if you can borrow one), ride the route early on a weekend morning. Check that there is someplace to lock the bike at/near the school, because you need to securely lock it. The lock deters a thief by making it more difficult, not impossible to take. The more expensive the bike looks, the more formidable the lock should look. If the front wheel has a quick-release skewer, you should secure it so something like or this

I strongly recommend a helmet. They all meet the same standards, so I buy less expensive.

There are lights that help make you visible and those that help you see the road as examples, but not recommendations.

You've thought about rain for your backpack, but you may want to consider for you too, because being soaking wet at school is no fun, rain jacket, rain pants and fenders. I have a pair of these which might be a good choice if you can carry other shoes to wear in school. Even without rain, it will seem colder when you are going downhill in the morning, so I use running gloves (full finger) some winter mornings. You can bundle up toasty warm for the mornings because you don't have to pedal that much, and then carry some of your clothes instead of wearing when you ride home, so I recommend a rack and a couple of bungee cords to help with that.

Since it is a walk-able distance, you should probably leave the water bottle, multi-tool, patch kit and pump at home on school days just to keep it simple and keep from losing those things. It probably makes sense to keep it minimal and cheap while starting out like this. If you get a floor pump with a gauge, you can use it to check the pressure once or twice a week and then learn how to feel the tires to see if they are firm enough. I've not found a mini-pump with a gauge that is universally regarded as reliable, so the pump I take with me has no gauge.

For your commute to school you shouldn't need to fuss with padded biking shorts or spandex shirts or even fingerless gloves. I rode quite a bit when I was your age without any of those. If you are looking at longer rides, then you might want to try some of those (no underwear under the biking shorts) to reduce chafing against the seat and wind resistance from floppy clothing.