Basic medium help

i was just wondering what the best medium to transplant my seedlings just about to enter vegetation would be.. preferrably cost efficient.. im not very good with chemicals or nutrient regimens and was hoping some people would have some good suggestions for a good medium that already has all the needed nutrients for the plant to be successful and strong for entirety of the plants life if possible .. thank you in advance

Basically something i just pop the plants in.. provide light.. water regularly .. keep warm and cozy.. and let grow