Best type of bike to buy?

If you plan on racing, you have to be very specific about the sort of race you will do. If you race on the road, your bike will not be suitable for riding across fields. If you do a mountain bike race, your bike won't be very good for riding on the road. There is no universal bike, especially so if you are looking at competing where the bike has to be entirely suited for the competition, unless that is, you don't plan on being competitive. You might look at cyclocross bikes that do pretty well on the road, pretty well off road, and are great if you want to do cyclocross racing

The closest thing to a "universal bike" would be (IMHO) a CX (cyclocross) bike. But you wouldn't win any road races on one.

YouTube video from about a year & 1/2 ago.
https://www.youtube.com/watch?v=j7RovOF6FSM

There is no such bike in existence for all conditions. As others have said, the closest thing to it would be a CycloCross Bike. You'll need a fairly big chuck of change. http://www.fujibikes.com/bike/details/cross-152

What kind of races? There's road bike races, mountain bike races, CX bike races, BMX bike races & so on. There is no do-it-all bicycle.

Toss in one more vote for a CX (cross) bike. They start around $1,200 to $1,300. http://www.raleighusa.com/bikes/road/cyclocross/rxs

There is not one good bike for that but it is ok to have more then one.

Go for a 700C hybrid mountain bike as with the endless parts online you can make it a drop bar road bike, cyclocross ,tourer, traditional you name it the hybrid is the truly universal bike. Have converted my own and others for different uses. Have one converted to a 'forties single speed replica the other is a traditional 'seventies style bike plus built a road bike tourer for a local lad. An old man has his fitted with road bike wheels, tyres and tubes of my Cannondale road bike as wanted better wheels for myself and his were written off.

No there isn t, you will need to settle on one thing or just chose one type of riding, or buy several bikes. Closest thing is Cyclocross but that is expensive and not good for road/track racing.

Mountain bikes are really good. They can be used on roads, and function really well. Don't have to buy really expensive, if you want to save money second hand would work great. Have fun biking!