The SKS rifle really is one of those situations where the less aftermarket accessorization, the better - in spite of the huge aftermarket in gizmos for it.  In particular, the long add-on high-cap magazines generally are unreliable and troublesome - so avoid them.  It's also a rifle really not worth scoping - due not only to its inherent inaccuracy level, but also due to the rainbow-like trajectory of its ammo.
   About the only worthwhile accessories for an SKS are the  inexpensive ones that make a big improvement: a peep/ghost-ring rear sight to replace the abysmal factory rear sight, a fiber-optic front sight for easy use in dim light, and a fistful of those 10-round stripper clips to quickly reload its factory 10-round magazine.  All of these things are available inexpensively from Internet Gun Show for about $50 total - less than a scope and mount for the rifle sells for.
   Only if your SKS has a really bad stock is any more money worth spending on it for accessories; polymer stocks of various kinds are widely available inexpensively.