Bring more circulation to your scalp, especially within the same hour that you take nutrients.
Whenever I want to grow my hair quickly (if I've cut it), I use a scalp massager that I bought on Amazon and I take cayenne pepper, Viviscal, biotin and msm.
Protect your hair by using a satin pillowcase to prevent breakage.
Make sure your protein/moisture balance is on point. Look into protein treatments and co-washing. This helps to ensure healthy hair and length retention.
Edited - As far as a topical, Wild Growth Oil still works well. I don't want to recommend any expensive products, because I don't know your budget.
You can reach your goal with the aforementioned methods and products.