Everyone should have a spice cupboard. This is mine:
It's like a store cupboard, only with spices. Like a spice rack, only much bigger. You don't need those piddley little jars with no flavour (please ignore that paprika one in the picture - emergency situation), you need a good big jar. Save all your empty jam jars (or pasta sauce jars, or coffee jars). Wash the label off (or not, it's up to you). Make sure they are dry, then fill up with spices from your local Indian/Turkish/Greek grocery store. If you buy them in packets (hence the need for jars, instead of clothes pegs), then they are much cheaper that those little piddley ones I've already mentioned. I use the TRS brand - cheap enough and good quality - and conveniently stocked in my local shop. Do label them though, otherwise you might accidentally chuck four teaspoons of chilli powder into something for the kids! Keep the jars tightly shut and they last about a year. And you always have something to spice up your dinner (even if it's just a store cupboard jobby). Your home-made curries with be more authentic than ever.
Essential Spice Cupboard Fillers:
Hot Madras Curry Powder
Hot Chilli Powder
Cumin seeds (so you can roast them and grind them)
Ground Cumin (for when you are too lazy to grind the seeds)
Coriander Seeds (see cumin seeds)
Ground Coriander (see ground cumin)
Hot Smoked Paprika (the Spanish version)
And if you are lucky enough to have some growing space on your window sill, get some fresh herbs:
You'll never need salt and pepper again! (Though I would keep some of those too).