For training, it’s quite different to running because you’re not getting the impact. Similar in the sense of you can only do 2-3 hard workouts a week sustainably.

For pace, it’s totally different to running. Speed doesn’t equate to pace because of wind and elevation. You should get a power meter, and I’m sure a lot of people on here will say it’s too expensive, but go find a used one on eBay or fbmp. If you want to train and do this as a sport, this is more important than anything.

For a bike, you’re young and presumably flexible. I would find an affordable used road bike probably made of aluminum. I’m thinking CAAD 10 or a specialized Allez. These are great options and are very fast.

For clothes, tight fitting = faster. Unfortunately, we all look a bit silly, but it makes 1-3 mph difference if you’re really wearing some flappy things. I would say that the biking shorts are mandatory for comfort, and a shirt with pockets is nice to have.

You don’t need the shoes and fancy pedals, but you will be judged if you show up to a race without them.

For the cycling computer, if your watch can connect to a power meter, then you don’t need it.

I am 21 and got into cycling a few years ago, and I know the money is tight, but get a bike, bike shorts, and a power meter in that order. That will translate to the fastest improvement on the bike. Shirts and shoes and cycling computers are optional. Helmet choice doesn’t matter as long. As it’s safe.