Gift for BF

My boyfriend (21FtM) is going to start T at the start of fall and I wanted to cheer this moment and find good serum for facial hair growth. What are good ones (including price/quality balance) and if it's a good idea to begin with? Maybe I missed some info about hormones and it wouldn't work, or too much stress on the body/skin etc. Also important to note that he has acne, so maybe aggressive ones isn't a good pick