How you go about making music such as this? (weeknd, fka twigs, banks)

[Callmeyeshua]

I'm really digging the ambient rnb (i guess thats what you would call it) sound, but as a person who primarily samples I have little idea of how to go about constructing songs that sound like this. I think if I could just find the base pad or melody these things are built of it would help a great deal but whenever i go into my DAW and try it sounds like trash. maybe my chords are just off or I'm not using the right sounds. It would be a great help if people could throw some insight in here.

example

 

[bandcoach]

it seems simple enough on the surface

I know that all of those sounds are in the stock library of patches for reasons synths and drum machines

repetition of notes is the key to this particular track/genre and the harmony is bare but made by the meshing of the upward bass line and downward moving synth line - i.e. Am-G[sub]/B[/sub]-Em-D is whet I am hearing first up (could be a different key (G#m) guitar sounds out of tune but want to finish this rather than spend a few minutes fixing that

 

[Callmeyeshua]

so basically this sound is just picking the right instruments even more so than other things? Since when I try to replicate I just get a mess. how would I go about choosing teh correct sounds and such to even start on making a track such as this?