If you don't mind the scale, then I would get the majority of the cast in their First Edition forms, since they're less kibbly and are just awesome toys in general. The RiD versions have simpler transformations (which can make it more fun to play with) but more fake parts.
To answer your question:
Wheeljack - RiD Deluxe
Optimus - First Edition Voyager
Soundwave - RiD Deluxe
Megatron - First Edition Deluxe
Starscream - First Edition Deluxe
Vehicons - one of each version? (FE, RiD, Jet Vehicon - personally, Jet is my favourite)
Smokescreen - Beast Hunters Deluxe
Ratchet - RiD Deluxe
Bulkhead - First Edition Voyager
Bumblebee - First Edition Deluxe (there was a Shadow Strike Bumblebee in Wave 4 but it doesn't match the new colour scheme)
Shockwave - Beast Hunters Voyager
Basically, if the character has a First Edition toy, grab that.
"sometimes the things you see might not be real and the things that are real you might not see"