An inexpensive starter kit is gonna cost $20-40,Depending on if you are ok with tube or want a box. Then you need to buy juice. There are some good inexpensive brands, I like Mtbakervapor.com, it's about $8/30 ml.
Tube style starter kit - they are fine, I started on an ego, they've gotten better since then.
This is a decent starter box, internal battery is cheaper to start with, but when battery dies, mod is done...
Another good starter box, the tank on this one is pretty versatile.
Replaceable battery box. Downside here is the extra start cost of a battery and charger ($12 for single batt charger+ $8 one battery), but a great little kit.
Factor in replacement coils, extra battery(s), juice. I would say low side to start out, bare minimum $50 for:
Tube mod
2 bottles juice <$10 /30 ml (don't buy "premium" $20+ bottles)
5 pack coils
I say get 2 bottles, so you can get one in high nic (18 or more) and one in 0, and adjust to what feels right.
Also note, while all my links are for one site, there are tons of places with similar, possibly better pricing.