A simple slime to concoct uses glue and liquid starch
(you can find it in the laundry aisle)
You can find people using all different proportions, but I use about equal amounts of each (I eyeball it) poured into a cup. You can add food coloring to the mixture as you desire. Stir until things gel up (if it's too sticky, add more starch). Then you can knead it with your hands. (You can rinse off any extra starch). As you play with it, it will become more smooth and gel/putty like.
You might also want to try using clear glue
, with or without food coloring for a different effect. 