If your hands are going numb, a simple thing to do, would be to replace the grips with an ergonomic type, Ergon, Specialized and others do these.
If you are getting a lot of discomfort after only an hour, this could indicate that the bike is the wrong size for you.
Would caution on spending much money on upgrades, as this is a low end bike, and you could quickly spend more than a new correctly fitted bike would cost.
Also, as you are internet shopping only, and appear not to be familiar with bike parts, this will more often than not result in some items being purchaesed which don't fit as expected.