I have heard a couple different main approaches. Some suggest potting soil, while I've heard some suggest using sphagnum moss and perlite/vermacile.
Potting soil has the benefit of not needing to disturb the roots when replanting.
If using sphagnum moss, what would you use for your first transplant? Potting soil and compost mix? Anything else?
Most seeds will do just fine in potting soil. That's usually the cheapest and easiest way to go, just fresh potting soil. You may even mix a little bit (5-10%) of perlite through it but it is not necessary. I sometimes do it just because I have it anyways (perlite).
But not all seeds are the same, some crops do need special instruction for germination. Please find out first the special instructions of the crops you want to sow (for example about how deep, how much (indirect) light, how warm, etc.). These instructions are usually more important than the substrate.
