Sulfer is one of those micro-nutrients that is only added when the soil is lacking it. Clovers and Alfalfa do need some sulfer, but an extra soil test is required, or your plants can be sent in for analysis of deficiencies. When planting clover, I'm mainly concerned with raising the PH with lime up to about 6.5 so the clover can use the applied potassium and phosphorus.

Gypsum is usually added when soils require sulfer. Gypsum does not adjust the PH like lime, but it is a calcium and sulfer source.