Heat/Light
All reptiles/amphibians have particular heat and light requirements. It will be your responsibility to research these specific requirements before aquiring your new pet. Heat can be managed by a few sources, depending on your reptile and it's enclosure. You can make use of heat mats, ceramic heat emitters, basking bulbs, or a combination of all of these depending on requirement. These will need to be controlled via a thermostat or a timing system, to emulate real world temparature gradients. Lighting is just as important too, more so as most reptiles require UVB lighting, which helps create Vitamin D in reptiles, which in turn helps them create calcium. Without it, most reptiles suffer from bone diseases brought about from calcium deficiency. It is also important to amke sure your lighting is on a timed system to properly simulate day/night cycles.
Diet
All reptiles have differing diets, depending on their natural habitat. Some are insectivores, some are herbivores, some are carnivores, and some are a mixture of 2 or more of these. Incorrect diet can lead to stunted growth and diseases brought upon by deficiency in key nutrients. As well as with the carnivores, you would want to aim to make sure the prey is not live, only frozen thawed, as live prey can cause damage to the reptile while feeding, sometimes severely, so it is best not to take the chance. With insectivores/herbivores, you can purchase these from your local supermarket/pet store, however you can just as easily cultivate your own supply with very little resources required.
Enclosure
The enclosure is one of the most important aspects of keeping a reptile, as in most cases you cannot simply leave them free roam around the house. Which enclosure you get will depend entirely on the reptile you hope to keep. Reptiles have minimum sizes for enclosures to make sure that they have enough space to feel safe and secure, and also get enough exercise, even reptiles can get fat! The material you would want to get is dependent also on the sort of heat ranges for your reptile, the required humidity, and also if you need to add a large body of water for some semi-aquatic reptiles. The enclosure and the light/heat sources aremost likely going to be the main bulk of the cost once setting up your reptile, so it is important to diligently research your pet's requirements.
Buy/Adopt
When you are ready, after doing your research, to be in the position to get your new, possibly first, reptile, there are a few main ways to get them. Most people would like to go to a pet store, so you can see the animals up close, and this may be useful to see if the shop can recommend any tips on keeping your pet fit and healthy also. There is a possibility that the pet store may not have the best information on the animals they keep, so it is always best to do your own research. For more experienced keepers, it may be beneficial to adopt a pet, and you can find these on local selling sites, social media, and possibly pet store owners may have a list of those who are looking to rehome their reptiles. This is only recommended if you are experienced with reptiles, as they may come with some health/behavioural issues which may take time and money to invest into your new pet.