the seeds were probably old and thus, the plants fragile. my recommendation is, for your first time, buy small already started plants, bring them home, and leave them in their pots for 30 days, then repot them however you want... either in a suitable place outside, in a big container all together, or in larger individual ones.
it is totally cliche but your best bet really is miracle gro soil, and if you want to go all natural, fish emulsion.