Extra Virgin Olive Oil
Sunflower Oil/Rapeseed (Canola) Oil
For asian cuisine: peanut and/or sesame oil
In terms of spices, I always have:
black peppercorns (in grinder)
some others that have slipped my mind too. My cupboard is chockablock.
The easiest way to do this is to find some recipes you know you like and keep those spices/herbs/oils on hand. Then as you delve into new recipes, you can add the seasonings from those recipes. This way you aren't overwhelmed and you'll actually use the ones you buy.
This is my short list of must haves:
Extra virgin olive oil
I use a lot of other stuff beside those, but those are the bare basics that I can't live without. Also, having lemons, limes, and some different vinegars on hand is really helpful.
"Luminous beings are we, not this crude matter." --Yoda