Complete kits here run £6.99 to £12.99, and none of them are toys; several are the same devices experienced vapers carry daily. Add £3.99 for a bottle of nicotine salt if the kit is refillable. Spending more buys screens and settings, not a better switch from smoking.
Three things: a kit, nicotine in the right strength, and a USB-C cable you probably already own. For a 20-a-day smoker that means any kit on this page plus a 20mg nic salt; ten-a-day smokers usually settle at 10mg. That is genuinely the whole shopping list.
Prefilled kits do; the pod arrives full and you vape straight out of the box. Refillable kits ship empty, so add a bottle to your order. If in doubt, the product page for every kit states what is in the box.
The battery unit lasts months to years. What you replace is the consumable: prefilled pods when the liquid runs out, or pods and coils every one to three weeks on refillables. A £7.99 Gotek X still going after a year has cost less than a week of smoking.
Match your habit, not your ambition. Twenty a day maps to 20mg nicotine salt; around ten a day to 10mg; social smokers to 5 or 6mg. Starting too low is the most common reason a switch fails, because the cravings never quite go. Step down later, once cigarettes are gone.