I always start by re-wrapping the handlebars of a new bike. I take thin foam material and wrap the straight sections to increase their diameter before adding standard bar tape. The thicker the bar the greater the contact area for my hands. I also shift my hands to various places on the bar and do not keep them in one spot for long periods of time. I even sit up on the saddle at times to take all of my weight off my hands.

If there are bike shops or a REI store near where you live I suggest taking the time to drive to them and try on their gloves.