Although we recommend the 3-product system for maximum benefits, if you choose only one product, start with the PurePlenty Nourishing Scalp & Strand Serum, since this product contains the highest concentrated level of Ajuga Plant Stem Cells and Saw Palmetto, to suppress DHT and promote healthy hair environment and cycle. We recommend that you use along with the PurePlenty Exfoliating Shampoo Treatment to prep the scalp for the Nourishing Serum.