Do NOT getThe Rainmaker, Adam and Eve or The Sum of No Evil until you have most or all of the others.
You pretty much cannot go wrong with any of the others:
Flower Power (where I started)
Paradox Hotel
Space Revolver
Retropolis
Stardust We Are
Back in the World of Adventures
Unfold the Future is great, too, but it is a bit fusion-y at times, which is maybe why you are not digging it at first. It is not as blatantly symphonic proggy from start to finish as many of the others.