when you say wifi do you mean the watch will be connected to your home wifi or your phone used ad hoc or as a hotspot ?
smart watches like the gear 3 tend to connect to the phone via blue tooth rather than wifi and there are many alternatives on the market ranging from as little as £10 to the price of the gear 3
there are a multitude of Chinese watches that come in a couple of formats, there are the ones with the same or similar functionality as the gear 3 but they all tend to be based on the same chip sets
there are smart watches that take a sim and a memory card ( google DZ 09 ) which function as a stand alone phone or /and a communication device between your phone and the watch which will allow you to make or answer calls via the watch connected to your phone or fully independently via it's own sim but most of these do not have wifi
there is also the full blown android smart watches the are basically and android phone on your wrist with all the bells and whistles such as blue tooth, wifi , gps etc
these offer some connectivity with your phone but you cannot make or answer calls via the watch connected to your phone
the watch is more set up to be used as an independent phone rather than an accessory and the most it will do is receive notifications you cannot respond to them
again this is all done via blue tooth
if you are using something like viber via your home wifi and the watch connected to the home wifi this kind of smart watch will work as a viber phone, i imagine skype will be fine too but all sim call related stuff has to be done via it's own sim including SMS
the wifi calls bit has thrown me because most of these kind of watches connect via blue tooth
a little more info on what you intend using it for would be helpfull