Get a bench and it will give you the right support you need when doing focused sets. I bought one for £40 that inclines up and down and also came with a booklet of recommended exercises. I couldn't work without one. It sits in my home gym along with the other equipment I have and it's well used.
This one on Amazon is similar to the one I've got and for £50 it will do the job. It will incline up and down, plus it's got supports on the end for doing incline sit-ups, which I find invaluable as part of my core exerices.
http://www.amazon.co.uk/dp/B000N3T0RI/ref=asc_df_B000N3T0RI2814412?smid=A3P5ROKL5A1OLE&tag=googlecouk06-21&linkCode=asn&creative=22206&creativeASIN=B000N3T0RI
My fav dumbell exercises are:
1) Standard bench press
2) Seated (with bench supporting back) shoulder presses
3) back row. left knee on the bench, left hand on the bench and then pull the bell up from the floor (and visa versa)
4) tricep extension. lie flat on the bench and bring a single dumbell (holding it at the weight section) from your chest back to behind you head and drop it down as far as poss then back.
5) shoulder shrugs. standing up, with a bell in each hand.
6) preacher curls (bicep). using a bench which is slightly inclined.
7) standing tricept extensions (lifting with the bell sort of in the middle of you back and up)
8) lifting the weights from a bench, take them up to your shoulders in the first movement, then extend totally up. then back to the bench and up in two movements. You can lift them from the floor, but it will probably mess your lower back up for a good week and I wouldn't recommend lower back exerices with heavy weights to anyone that I didn't know how their back was to start with.
It's hard to explain on the net without pics. I'd just google dumb bell exercises. Try different ones and see which are best for you. I bet youtube has loads of vids.
I don't find doing flys with dumbells very effective, as you lose the weight's effect as you get them closer to vertical.
Just remeber that whatever exercises you do, quality sets are the important element. Full and controlled extensions of the muscles