murray, thanks; got it now
videoav, welcome to
RP.
all the things you mentioned in your original post are pretty much correct. the skin tones dont match, the images look cut and pasted and so on. it's also more desirable, usually, to narrow the overall image by putting each person closer together.
the best way for us to really help here would be to post the original pictures. or, maybe just post a few and start with just those. from there you could get the hang of it and do the rest yourself.
also in looking at your image i can see that you've done your extractions too close to the edges. it's often a good idea to add a bit of feathering to extractions which will give you a more natural look when pasted back. it can always be erased if it doesnt look right but much harder to add back if you left something out.
these are always a bit tricky. you also have to watch out for the size relationships of each object you extract. a few of the people look either too small or too large relative to the others. so either before or after (i usually do it after) you sometimes have to resize the image.
there are a lot of things you have to watch out for on these, relative size, the extraction(s), color balance and even relative noise levels, but most particularly lighting. and that one can drive you a bit nuts

still, it's most likely do-able. i really would like to see the originals if possible.
craig