Here's what I have done for years. It is relatively inexpensive, good for the deer, based generally upon recommendations of several ag universities here in the deep south. As already mentioned the deer will benefit from high content of both phosphates and calcium. I use a mineral often referred to as "Di-Cal". It is "dicalcium phosphate". Comes in 50# bags for about $20. I also use a high calcium mineral that is used to supplement dairy cattle often referred to as Hi Cal. It si about $15/50#. #Often times my supplier is out of this, so ... To these two I add "White Salt" (Na Cl). It is about $6/50#. All of this si bagged, not block. The mixing ratio I try to stay close to is 1 part NaCl to 2 parts Di-Cal and/or Hi Cal. The deer are naturally attracted to the Na Cl. They get the good stuff as they consume the mix.

I put about 100# - 200# of this at each lick area early spring and refurbish mid summer.