For a number of years I have struggled to find a good commercial potting mix that does not need additional product to grow in. Below is the 'recipe' I use and I have had great success with - from Hydrangeas to Roses, Herbs to Tomatoes and pretty much everything I have tried.
In a buildings tub I mix
I bag Manure (cow or sheep)
1/2 bag of Perlite
1/2 bag of Peat Moss
1/2 (9ltr) bucket spent coffee grounds
1/2 large block of Coconut Coir, broken up dry
2 (9ltr) Buckets of garden soil
1 handful of all purpose fertiliser granules
2 handfuls of Rooster Booster or Dynamic Lifter
The cost of the mix rates alongside the best of the commercial potting mixes but I find it much more successful for pretty much everything I have grown with it.
I mix the ingredients dry (including the coconut coir)