Some of these questions will depend upon where in the world you are. Also, all soils are different and all plants have different needs so fertilizer isn't a one-size-fits-all answer, either. However, plants want to sprout and grow. I have potatoes growing in my compost heap because apparently they weren't as done as I thought they were.

If you want a place to start, why not buy some young plants and try to keep those going? Just pick something that meets the sunlight and climate requirements of your area. Many will have tags telling you this information. Sure, it's a bit more than seeds, but it might pay for itself in produce if you succeed. Mint is basically a weed so, if you like mint, that might be one that could fit.

After that, you might see what works and what doesn't and buy some seeds. Best of luck!