Using worm castings as organic fertilizer for seeds, new plants or existing gardens is an amazing way to see maximum growth and reduce transplant shock.
When starting new plants or seedlings I use a 50/50 mix. 50% worm vermicast and 50% peat moss or coconut coir. Coconut coir is my first choice due to it being more neutral on the ph AND it is hydroponic (holds water).
At the farm where I teach worm composting classes, the farmer was in amazement last year when he first used the starter mix. This year he is using it for all his seed starters.
The worm casting mix provide nutrients, beneficial micro-organisms and require less watering. Talk about an all in one!
Some other options organics are: compost: traditional/mushroom/manure. Although vermicompost is the best of course!