There are really only four flavours you need for cooking and, fortunately, they all begin with the letter S. They are sweet, sour, salt and spice.
Sweet is obvious. Sugar and honey. But fruit is a good source. I don't eat fruit on its own (can't see the point of eating something cold and wet). But it's a great source of sweetness. Nothing like apple slices with pork. Or even in chicken soup.
Lemon and lime are your obvious sours. The fresh stuff is great if you've got it. And don't forget to use the zest, there's loads of flavour in that. But the bottles of concentrate are a handy and convenient option.
Salt is, well ... salt. But a stock cube is a good alternative. They're usually about 50% salt, but the rest is a nice meaty flavour that can add a nice kick when you need it. And soy sauce is another way to get a dollop of salt plus a little extra.
Spice is my favourite. I reckon any meal that doesn't clean your sinuses down to your boots isn't quite hot enough. Fresh, powdered or in a hot sauce, they're all good to me.
These four flavours, used in the right ratios, can make anything delicious. Just keep tasting until it's right for you. And if you're travelling light, as I like to do, you can stuff all four in your backpack without taking up much room at all.