If you want to have everything (or almost everything) that appeared from the Smurfs without collecting Spirou magazine and other books, the easiest way might be to buy the Rombaldi collection. In the late eighties (starting in 1986) they made a beautiful collection of everything Peyo has made in 11 volumes. The first five are dedicated to the Smurfs, and include many otherwise unavailable comics and versions, Smurf stories, a guide to learn to speak Smurfs, .... I don't think everything Smurfy is included here, I think the publicity comics aren't there, but since I have only one part, I may not be the best judge of this. They regulary turn out on Ebay Belgium and France, for some 15 or 20 Euro for a volume. The last volumes (no Smurfs) fetch higher prices, as they were printed in lower numbers. For example
here you can see what they look like and what price they fetch. Don't rush to buy it, they are not very rare so you can look for a good price.
There are also many other Rombaldi series (Tintin, Asterix, Yoko Tsuno, ...), all equally good although not always equally interesting (there is less rare and unpublished stuff from Yoko Tsuno, for example).
Bored of normality, why not go smurf? 
), King Smurf, and Smurfsoup 
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