hello and welcome to ecf
a few more questions
are you looking for vv/vw (variable voltage/wattage)
are you looking for internal or external batteries (internal are nice because they tend to be smaller, but once the battery is dead the mod is useless, whereas with external, just get new batteries)
do you want tc (temp control) you don't have to use it but it is an option and they tend to have firmware upgrades
do you want something more pen/cylinder style or box style?
Are you wanting something small and discrete, or something a bit bigger (single battery, dual battery, triple battery)
what is the most you'd be willing to spend
are you just wanting a mod or also an atty (do you want a tank or dripper and are you looking for more of a mtl (mouth to lung) or dl (direct lung) )
ebay while sometimes cheap isn't really always reliable, and especially because vape items aren't allowed per their TOS, so buy at your own risk.... there are many other places that are cheap but be prepared to wait a month on delivery (fasttech (is awesome just to browse as well, they have lots and lots of stuff), aliexpress, 3fvape, 3avape, everzon, eightvape (be careful though their customer service sucks, great prices but if it's doa they usually don't care) )