Originally Posted by Mikefule

Proposed 50/16 = 3.125 (multiply this by wheel diameter to get gear inches.)
Current 48/15 = 3.2

3.125/3.2 = 0.977

Proposed ratio of 3.125 is 97.7% of current ratio of 3.2

Ths means that your proposed change of ratio will make about a 2.3% reduction in your ratio.

This is negligible: a marginal lowering of your gears. For comparison, on a derailleur bike, changing between 11t and 12t is roughly a 9% change.

In order of value for money that you will feel in the performance of your bike:

1) Get the best tyres you can afford.
2) Get the best wheels you can afford. Aero for going fast and steady speed, light for anything that will require bursts of acceleration such as city riding or hills. Aerodynamics become more important the faster you go. Weight is important every time you need to overcome inertia or gravity. What works in the context of a track or time trial may slow you down in the cut and thrust of a commute, for example.
3) Get a new chainset only if you can detect anything wrong with the one you have, or if it is incompatible with the ring size that you need.

In order of value for money that you will optimise your gear ratio:
1) Ask yourself whether you really need to change your ratio, or are you just tinkering for the fun of it.
2) 1 tooth on the sprocket makes more difference than 1 tooth on the chainring. At the sizes that you'e talking about (around 48/15) one tooth on the front makes 1/48 difference to your ratio (say 2%) and 1 tooth on the back makes 1/15 difference (say 7%). The effect of changing both for bigger, or both for smaller will be that the changes tend to cancel each other out.

Of course, change for change's sake, and pimping your ride is legitimate and we've all done it from time to time, but if you're looking at genuine performance gains and good value on a budget, you need to think about it realistically.