Alien comes in at a good price point. Takes 2 batteries and reportedly does balanced charging (however, I almost always go the external charger route unless a built in battery or something like a DNA board made for in mod charging), comes with a Baby Beast which folks seem to really like. I have the mod itself, without the tank, and am quite happy with it.
A step up is a G Priv. Same power as the Alien, also 2 batteries, but has a touch screen if you like that sort of stuff, but that is just bells and whistles. Comes with a Big Baby Beast, which uses the same coils as the BB, but the tank holds ~4-5 ml. Both will come in under $100.
Something more maybe a Minikin 2, also a touch screen, then add a tank. For a step up, and for excellent temp control performance if you ever get into it would be a DNA based mod. You can get a 166/250 2 or 3 battery mod anywhere from ~$120-$150. Then add a tank. If you want factory coils, maybe the Baby Beasts mentioned above, a Freemax Starre Pure which uses ceramic coils that last a long time and can be cleaned up, or something simple and inexpensive like a Tobeco Super tank which uses Atlantis compatible coils, meaning lots of choices in the market. It's also very reasonably priced. That would be a bit more up front (a quality battery can be had for ~$5 each from a reputable vendor, not eBay or Amazon) but I would feel confident charging in a DNA based mod, so you would save the ~$20 for a decent external charger.