I will tell you that not everyone is the same. It's all part of the genetics. Some people can build their chest faster than others but in the beginning it is the hardest. You don't have much of a chest therefore when you do any chest exercise, it's almost impossible to contract them and squeeze them at the top which is the most important part next to getting a good stretch. What I would suggest you do is start off with dumbbells. Don't listen to anyone else saying to use a bench, because if you want to build your chest whilst benching, you need to have good form. It is absolutely imperative to have good form and it's very difficult to perfect the bench press.
So, as I was saying go with the dumbbell route. Since you're a beginner I would assume, go for a moderately heavy weight where you can get only 8-10 reps. The last rep should be very hard to complete, if you go over 10-12, bump the weight up. 3 sets of 8-10 on flat bench, and 3 sets of 8-10 on incline. Then after that you should do dips with a little bit of a forward lean to hit your pecs as well. That serves as a substitute for a decline bench and it's actually a lot more comfortable for most people.
