A different gear ratio may help you pedal more comfortably, and maybe a bit more efficiently for your terrain. A different crank won't make you more efficient unless you're already straining the limits of your current setup. You'll only get stronger by riding more. As for the bars, if you want efficient, you want drop bars. They give a more aero riding position. I'm not sure what you're looking for with the brakes. You won't notice any weight differences there. You might shave some grams with the carbon fork, but it would be a bit ugly on that bike, and not really worth when the rest of the bike is straight gauge CroMo steel. Finally, the hubs and wheels. Unless you build your own wheels, it's probably easier to get some that are already built. If you get a much lighter set, say the ~ $300 Sub15 wheels from Wabi Cycles, you may notice a difference here. By the time you upgrade all those parts you're looking at more money than the bike cost to begin with. If you're on a limited budget you're not likely to end up with parts that are better than what you already have.
tl;dr - unless you feel an obvious deficiency, just ride your bike. You can put money away over time and buy a whole new, better bike when you're ready for one.