The vivarium should be set up before getting the gecko to ensure that an ideal environment can be achieved.

This is what I would suggest you need to set-up a vivarium for 1-2 geckos other people may well do it differently. But this is what I use and it works for me. Most of this equipment can be purchased from any reputable reptile shop and some can be made yourself try looking at some of my links

Equipment

Vivarium (glass or wood)
Heat mat
Thermostat
Thermometer (x2)
Lamp holder and Bulb
Timer
Substrate
Hide
Moist hide
Water bowl
Calcium dish
Mealworm dish
Decoration

Vivarium
There are pros and cons to using either glass or wood but I personally only use wooden vivs for my adults. Wooden vivs are in my opinion easier to control the heat in and you can also stack them should you need to.
You will need one at least 24ins x 15ins x 15ins being that your gecko will spend most of its time on the ground you need as much length as you can give it rather than height. (see picture below).

Heat mat
Being terrestrial leopard geckos absorb heat through there underside so therefore you need to heat the bottom of the viv this is best done using a heat mat. It should be placed on the bottom covering at least one third of the viv. (see picture below)

Thermostat

If you didn’t all ready know thermostats control the amount of heat the mat puts out.
You will need to set the thermostat up to heat the substrate up to between 83F and 87F. (see picture below)

Thermometer
You will need two of these one placed at the hot end and one at the cool end

Lamp holder and bulb

This is not a necessity but it can serve two purposes, it can help to raise the air temperature giving the impression that its day time as the air temperature in there natural environment would be higher during the day and it would also help you to see your geckos. I always use red bulbs, as the geckos cannot see red. Lamp holders can be purchased at most diy shops for a couple of pounds you will need to buy a bulb the wattage will depend on the size of the viv I use 15watt pygmy bulbs in my 2ft vivs and 25watt ones in my 3ft vivs it’s a bit of trial and error. (see picture below)
 

Timer

You will need this to turn the bulb on and off to get your day night cycle

Substrate

There are at lot of arguments as to which substrate to use so I am not going to far with this only to say I use calci sand and I have never had any problems. If your unsure which one to use visit lots of web sites read lots of books and talk to as many gecko breeders as you can that’s all I am saying on the matter.

Hide

You will need somewhere for your gecko to hide this is where it will spend most of the day. Your gecko will get less stressed if you supply at least a couple of places to hide. You can make a hide your self out of old margarine tubs (see picture below) or buy one of the many ready made ones on the market. (check out my links page)
Moist hide
You will need one of these it helps when your gecko needs to shed its skin. Either purchase one or make your own out of an old margarine tub just put some damp kitchen towel in it or use dampened moss. (see picture below)

Water bowl

These can be purchased from any good reptile shop. (go to my links page) This is the one I use for all my adults. (see picture below)

Calcium dish

A small dish of calcium powder is a must as your gecko can help its self when required. This should help stop your gecko from deliberately digesting the substrate.
You can use old plastic milk bottle tops I use the tops from my cider bottles mmmmmmmm cider (see picture below)

Mealworm dish

This needs to be of a kind that does not allow the worms to escape these are available from most good reptile shops this is the one I use (see picture below)

Decoration

There are hundreds of plastic plants vines and background available. I would suggest not using real plants as they will need watering which would raise the humidity to much besides some of the plastic ones look fairly real any way. You could use bark bits of branch but dont put to much in so that you cant see your gecko for the decoration.