Where do I start? Try a DIY kit from greenbeans. And then maybe download the pattern from TNN (the webpage not the forum part)
What sorts of fabrics do I use? Generally speaking, no you can't use spotlight. There are a couple of fabrics there you can use but for starting out I'd go with
Greenbeans. They have everything you need in the one place.
Can you make a OSFA? Of course you can. If you can't find a free pattern for one though you will have to experiment and come up with your own.
Do the patterns include inserts (or whatever you call the 'things' you stuff the pockets with)? I'm not quite sure what you are asking. But the things you stuff them with are inserts. You can make these from microfibre (again check out greenbeans) or you can just buy them ready made.
Do pockets need covers? No. Most pockets are made of PUL which has a waterproof layer.