Take a look at their website and see what appeals to you off the bat. They are all good solid knives. In my opinion the Delica is the heart of the spyderco line, being a lockback, vg-10, with FRN handles over steel liners, with the big ole opening hole
But the Caly is also one worth looking at as the choil is quite an interesting feature.
And the Native should never be over looked, as if I remember right its the one that started the idea of spydercos being "designed in the dark" aka very good ergonomics but pretty funky looking.
Again you really can't go wrong with any of them, but if you have the cash to spend, I'd suggest staying away from the tenacious line, as the lower end steel can leave a bad taste in the mouth for some people.
My order of purchase went like this:
Tenacious (they had just come out, and my ex g/f surprised me with it)
Delica 4 ZDP189 ( I love british racing green...)
Ladybug Salt (To try out H1 steel)
Tasman Salt (PFD knife)
Another Delica 4, this one all black and combo edge I found on ebay for CHEAP
I've tried most of the offerings, good luck deciding, its not easy lol