I started with an SKS, and have since gotten a cheap sporterized lee enfield. I still want a swiss K31 and a swedish 1896 mauser too. And a Mosin Nagant. I got the enfield cheap, otherwise I would have gotten a Mosin.
If you dont mind it being a sporter, a cheap enfield is easy enough to get. Mine was $142 after shipping off the EE, and shoots plenty well enough for the price. Its going to be my short range bush gun, because it'll cost more than the rifle was to get a scope mounted. Even without a scope I would feel plenty confident with its accuracy out to 100 yards with the iron sights.
If you want something semi auto for a plinking toy, the SKS is hard to beat, especially considering the price.
Price is another thing to consider. Both the price of the gun, and the price of ammo. The red rifles (SKS and mosin) have plenty of cheaply available milsurp ammo around. The K31 also has the GP11 ammo widely available, and is VERY good quality for milsurp ammo. So good that apparently people use it for competition purposes in switzerland (Or so I have read on the interwebs. who knows...) The GP11 ammo is much more than the stuff for a Mosin, but its still much cheaper than regular factory ammo.
You can also still find milsurp 8mm mauser ammo, but its not so common and not so cheap.
Finally, others dont have much milsurp ammo around. You might find some 303 british milsurp at a gun show, but its unlikely to find any in a store. I know nothing of 6.5x55 ammo, but I haven't seen any milsurp ammo anywhere so its probably uncommon to nonexistent.
Long story short, it really all depends. How much do you wanna spend on the gun? How much do you wanna spend on ammo? Do you want something that'll be good for hunting? Or just a target gun? Do you want it to be a pristine example with all matching numbers and full military stock? Or is a sporterized model acceptable??