The difficulty of Spider Solitaire varies greatly depending on whether you decide to play with 1 suit, 2 suits, or the nightmarish 4.
The basic premise of spider solitaire is to build a sequence from King to Ace (descending order) of the same suit. When you complete a sequence, that sequence of cards is removed from the table.
If you’re just getting warmed up, start with 1 suit. If you play with 2 or 4 suits, things get a bit more complicated. Inside the tableau you have the option to place cards sequential by any suit, however, only cards of the same suit can be dragged as a group (and of course, only Kings -> Ace of the same suit can be removed), so you want to be careful and strategic as to how often you combine different suits.