Math Manipulatives
Traditional Math Manipulative allow students to have visual less abstract experiences with numbers.
Counting Bears
A set of Counting Bears of with 60 Bears will be good for about 5 students assuming you go up to sums of 12. Therefore order about 5 sets for class.
Unifix Cubs
A class set of set of 300 Cubes would allow a class of 20 students to have 15 cubes to work with each.