A young friend of mine recently asked me how he should get started in "real cycling." He is in his early thirties, and has been riding an inexpensive mountain bike to lose some weight and get in shape. He has lost significant weight through dieting and doing some riding. He tells me that he enjoys the cycling, and would like to do something like Cycle Oregon, a week long ride that covers four to five hundred miles. He is wondering if he can do it on a mountain bike, or should he get a better bike, or a road bike as he knows that Cycle Oregon will climb about 20,000 feet. He admits that he does not know, long term, where he wants to go with this. I tell him that I did not know where cycling was taking me either when I did my first organized ride, the infamous Tour de Chicken in Peoria, Illinois in 1995. That was close to 200,000 miles ago, and numerous bikes which became lighter, and more specialized with time. But here goes with the advice you asked for. These are only my opinions, but are based on my own trial and error which eventually led to some plan that worked-for me.
1. The bike. Don't spend under $1000. You will get a bike that is heavy, not very comfortable, unbearable climbing, and with parts that don't function the way that you will eventually want them to. In a short time you will be disatisfied. A better bike will keep you motivated. For components you want Shimano 105 or better. This is the drivetrain and deralleurs. I have always used Shimano, but each component maker, Campagnola or SRAM have comparable levels. I prefer a carbon fiber frame, however, aluminum is making a comeback. Builders have figured out how to build with aluminum, making it stronger, lighter and more comfortable than early models. You can now get, for example, a Cannondale CAAD with 105 for around $1500. This bike was recently chosen by Cycling Plus magazine as it's bike of the year, over many top of the line carbon bikes. This choice was based on value, top of the line components and ride quality. You just get more for the price with aluminum. This is a bike that will last you many years as you develope as a cyclist, or feel the need to go even better. Specialized also makes an Allez model that is comparable, and Trek makes an Emonda as well.
2. Clothing. First of all you need a helmet, and again spend at least $100. You can get something with ventilation-you won't believe how hot you can get on a summer day, and it may be a helmet that will actually save your life. You will also, eventually want a jersey, again ventilation and pockets in the back; and you will want cycling shorts. A word on bike saddles and shorts. You're going to need padding, but not too thick. A saddle with thick padding starts to feel worse than a thinly padded saddle after 30 or so miles, and the same is true with shorts. This is trial and error, and eventually you will find what works for you. When you don't get it right a saddle, after fifty miles will hurt worse than anything you can imagine. Keep in mind that more is not necessarily better. Sooner or later you will also want to get cycling shoes, and clipless (clip in) pedals. I know that some cyclists think this unecessary and overly complicated, but the reality is that softer shoes like running shoes do not have a stiff enough sole, and you begin to have problems with your arch. Again shoes and pedals are trial and error.
3. Riding. I know that you know how to ride a bike. But this is different. The pavement is hard. Avoid colliding with it. A car is worse, in fact can be deadly. A good road bike, with a powerful rider is capable of 30 miles per hour on the flats, and as much as 50 on downhills. This is fast for a two-wheeled unprotected rider. This is so dangerous, yet such bliss when done with efficiency, grace and safely. Practice the skills needed, leaning in to a corner, carving a downhill, but keep your head up always scanning your surroundings, expecting that anything can happen in less time than you may have to avoid a situation.
4. Eating and drinking. These are both trial and error. Any ride longer than an hour will require fuel. You will find that it is advantageous to eat on the bike which could be gels or solid food. You will also want to find a drink mix that suits your tastes-water alone will not keep you hydrated for long. And a good drink mix will provide some nutrition. Yes, trial and error, but the dreaded bonk in the middle of nowhere can be your worst experience on a bike.
5. Mechanics. Learn to do as much as you can-it will save you money. In the least learn to change a tire. A flat 50 miles from home should not mean you need to be rescued. On the other hand, I doubt that I will ever be good at truing a wheel, or changing shift cables. There are some things that are better left to experienced hands.
6. Wheels and tires. Road wheels used to be very narrow as did tires. They are both becoming wider, the tires more rounded which has resulted in lower rolling resistance, and increased comfort as PSI can be decreased though volume is increased. Wheels will be your first upgrade.
7. So called endurance bikes or gravel bikes. Gravel races are big in the midwest. Many manufacturers are now make road bikes specifically for these events. They are not as light as the normal road bike, but are still efficient on pavement, and have the capability of using wide, mountain bike type tires for off road. This type of bike would also be a good choice depending on the terrain you imagine yourself riding.
That's all I can think of for now. To be continued.