If you’re not up for spending your money on one of the less advanced smart watch models, you may want to check out maker Jonathan Cook’s DIY Open-Source SmartWatch, part of which is 3D printed, something the prognosticators of future tech surely didn’t forecast. Cook shared instructions for making his SmartWatch on the webzine “Make:” and also on his own website, DoNothingBox. You can download the STL files on the DNB site, too. For around $125 or less you can make your own smart phone and you can customize it, something that you wouldn’t be able to do with a store-bought version.
This is a site dedicated to Linux and so I am of course going to recommend the Linux Mint option. The look and feel will be much like the Windows 7 interface you are currently using. You won't need to upgrade your hardware. You will never be out of support. It won't cost you a penny. You won't need to buy extra software such as Microsoft Office. You won't get any viruses.