what should i do and how long and how often should I do them for

i have only 1 dumbbell and i'm getting bored with push up exercise , so can i do one arm dumbbell press? can i lie on my flooor too becoz i dun have any bench and the most important is that does it has some disadvantage like one chest is bigger than others , LOL.

What are good weight lifting chest exercises to lose man boobs?
I already do bench press a machine, and flys.
I know I should be doing more but I just dont know what is effective.
I already know I should manage my diet so I just want to know the most effective exercises.

I am almost 16 and I have a pair of adjustable dumbbells, from 2.5lbs to 40 lbs. I don't want to bulk up too much and just want to build some overall muscle, and no weight loss.
I need dumbbell workout out or weekly routine which I can use to build muscle overall. I can also do bodyweight exercises.
Any information would be beneficial.

I bike 30-60 miles a week at a pretty good pace already but i read that it is a good idea to throw in strength as well as flexibility to your cardiovascular work outs.
Now I am a very skinny guy with all the biking I do already, but is the biking, dumbbells and standard stretching sound pretty good? Should I throw something else?
I'm on a budget so i figured those things should suffice.

and what muscles does the "dumbbell shoulders press" exercise benefits?

i'd like to work out my shoulders, back, and chest, but only have 1 dumbbell. What are some good exercises.