The classic old book "Soft Ferrites - Properties and Applications" by E. C. Snelling gives a lot of equations and theory about inductor and transformer winding design, in particular the very important proximity effect. I'm not sure if your newbie status will let you see this forum:
That book takes some effort to use. Newer books may exist with easier-to-use design guides. Or perhaps software such as Intusoft's "Magnetics Designer". Anyone have suggestions?