I use the stuff sold at Walmart. Comes in a gallon jug with built in sprayer. Pretty much spray everything in the shed. It dries clear and has done a great job of keeping out the bugs. Keep out the bugs and you wont have spiders.
Bugs and spiders and rodents in my shed are a major pet peeve of mine. Especially everyday house flies. They drive me nuts. I bought those little one sided sticky sheets and they work miracles for the flies. They are about 4"x 7". I stick them to the top corners of the windows in my shed, where flies like to congregate. Those pads fill up pretty quickly. But it's a never ending battle.
Another thing I did (call me ****) is a caulked all the little cracks and crevices in my shed. All the trim around the windows, where the cabinets meet the walls, where the base trim meets the walls, everything. I don't give the bugs a place to hide.