Budgeting for all of this before deciding on a species avoids the common trap of buying an animal first and then finding the full setup runs well beyond what was expected, often in the low hundreds of pounds once heating, lighting and furnishings are all accounted for.
The practical approach is to treat a kit list as a checklist rather than a guarantee. Before buying, it's worth cross-referencing what's included against a care sheet for the specific species intended for that enclosure, checking off enclosure, heating, thermostat, lighting, substrate and hides one at a time, rather than assuming the word "kit" means nothing further is needed.
There's also the simpler issue of gaps. When ordering from several places at once, it's easy to end up missing something that felt implicit, a second hide, a suitable water dish, the right substrate depth for a burrowing species, because no single order was ever checked against a full list of what the setup actually needs.
Putting together a first reptile setup from scratch means sourcing several different products that all need to work correctly together: the enclosure itself, a heat source, a thermostat, lighting, substrate and, for many species, a livefood supply. Buying all of these from one supplier, rather than piecing them together from several different retailers, removes a fair amount of the risk that comes with a first setup.
More information is available at
Reptile Centre UK.
Minimal handling is the starting point. However tempting it is to interact with a new arrival straight away, most reptiles settle better with little or no handling for the first few days, left instead to move around the enclosure and find its hides and basking spots in their own time. Handling can begin gradually once the animal is feeding normally and showing settled behaviour, rather than on a fixed schedule regardless of how the animal is actually responding.