Fleetwing did a good job answering your question in the new member introduction thread (I can't move an individual post otherwise I'd move it here). Without knowing which model you're referring to when you mention "Deluxe" (there were many of them), and assuming all three are in equal working condition, I would go with the SM3. You can't go wrong with the Classic 12, it's a solid, well-performing machine, but the SM3 has the edge in terms of build quality and more subjectively, in terms of aesthetics (I prefer '50s styling over the '60s but the opposite might be true for you). 

​Which of the three do you like looking at the most, and would like to see as a fixture on your desk? The bottom line is simple: that's the typewriter that you should pick.

 

I literally just got an SM3 deluxe two days ago (well technically last week, but just opened it) and I am impressed. I recently acquired 3 Olivettis a week or two before that. Hard to say which I prefer, but the Olympia is more solid and tank-like. I was quite impressed when I opened it. Looks nice too, with the dark green and chrome trim. It might be my go to typer. My only complaint is the carriage shift, but not that big of a deal, really.

When you say "case" are you referring to the travel case or the typewriter's case (coachwork, shell)?

If you're looking at these machines online you can always include a link to the page so we can positively identify them. 

How much you can expect to pay all depends on your location and the models that are more common to that area. I have five SM3s at the moment and the most I ever paid for one was $60, another was $50, and the rest were less than $40. Unless there was something very special about the typewriter, I'd never pay more than $50-$60 for any Olympia.

Two Olympia SM storage/travel cases for comparison:

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Uwe, I forgot to answer your question.  The one from the 60's has a case like your upper photo.  The one from the 50's has a case shaped like your lower photo but more of a tweed look, a different handle, and a different latch.

Since you're in the United States I'd suggest Staples for ribbon. I don't know if there's a store in your area, but if there is and they don't stock the ribbon, they can order it in for you free of charge. There are also numerous vendors on eBay and Amazon that sell what you need, generic 13 mm (½") typewriter ribbon.

​The pivot bolt for the line space lever might not be an easy find. I'd search online (eBay, for example) for someone who is parting out an Olympia SM. You might luck out getting one here from another TT member, but you might need some patience before one is found. Of course that's not to say that you can't fabricate something that will work in its place. 

​As a side note, what you bought is typically described as being a 'SM3', not a 'SM3 De Luxe'. You'll note that it doesn't say SM3 anywhere on the machine, so the De Luxe script was added to the segment cover to differentiate the machine from the more basic SM2 model. When you state it's a SM3, the deluxe classification is inferred.