the best way to get your soil mix equal is to take a quart size mason jar,add 2 cups water //1 tabelspoon of calgon water softner// 1 cup of your soil mix,after mixing shake the shit out of it ,to mix everything up. let it sit 24 hrs,after 24hr measure you sand it will be in bottom,next layer silt ,next layer will be on top that is compost. when using this method you will no what your lacking and can adjust by adding what ever your short on .idea of it all is to equalize your soil mix once you establish this ,you move on to a cheap ph and npk tester ,get on ebay 15 bucks,all self explained.
after you have established your goal you ready to roll friend,play ground sand isnt any good by the way ,get greensand it might not benifit you first grow but the idea is for aeration and to retain moisture.
i hope this helps both of you because it sure was a lot of typing for a smoker in the clouds