I'm glad the soil science question has been successfully solved. Recommending that a prospect buy another victim of the same genre is really good advice, too. What's that quote? "Doing the same thing over again and expecting a different result is the definition of insanity?" If it is too difficult to keep a juniper outdoors, then stop keeping Junipers and stop keeping anything outdoors until enough experience is gained to keep something alive for some reasonable period of time.
The question of proper growing media for this or that is disputed here constantly and we don't come to blows only because we can't find each other, and recommending that a newbee step into that morass right off the bat is... _ _ _ _ _ _. If I use the proper word here I'll make more enemies, so I'll let each of us fill in the blanks.
The OP needs to describe his apartment window situation, and his outdoor growing exposure, too. He needs to go back to the store where he bought his dead tree and make a list of what else they are selling, especially those trees that appeal to him. Don't ask for advice there. They already had a chance to sell him something that suited his situation and failed. Come back here, possibly with some cell phone photos and we'll kick around his prospects. It's worthless to discuss, "look for this or that species" without knowing what limited choice is available, and buying something from an online vendor is going to more expensive, so lets walk before we run as cheaply as possible.
