Bad reptiles/invertibrates for beginners
These are my top 5 reptiles that beginner hobbyists shouldn't own, they might not be the most popular choices but I firmly believe they shouldn't be geared toward beginners.
1. Bearded Dragons - While it's true they're very tame, easy to handle and feed well in captivity, I feel they aren't suited for beginners. These reptiles should be given to someone after they owned something simple like a Leopard Gecko or similar reptile. Their set up requirements are expensive and can be a pain to monitor, such as UVB and temperatures. Since they like it hot, the cost of lights and heating implements can really end up being a lot if you don't know what you're doing. Another issue is preparing their food daily, chopping up and providing a variety of vegetation. These guys prefer fresh food to prepared foods. They also require bathing to avoid dehydration.
2. Iguanas in general - Iguanas tend to have bad attitudes and grow very large in a short amount of time. They might be cheap, cute and little as babies but in a year or so they become big, mean lizards with expensive care requirements. They need huge cages when they get to be adults, not to mention you must provide UVB and heat for them as well as places to climb. Once they get very large some species feed on rodents and other reptiles. All in all they're expensive, aggressive and not a good choice for beginners regardless of their inexpensive cost in a petstore.
3. Hermit crabs - Yes they are inexpensive to own and maintain but since they are sold in places like malls, shopping centers and otherwise for extremely cheap.. most parents and children buy them on a whim. These impulse buyers have zero clue how to take care of these animals and end up killing them with their inexperience. If you have the proper knowledge before picking one up, they make excellent pets.
4. Tarantulas/scorpions - These poor invertebrates are often purchased by younger children or teens who have no idea what they're getting into. I've seen so many of these beautiful animals perish under the ownership of the aforementioned. They have relatively inexpensive living requirements and food costs which makes them popular. Plus what boy doesn't want a big bad spider or bug to scare his sister or other girls with? Unfortunately most don't know these pets don't enjoy handling and do tend to bite or sting, which usually ends up with the creature being killed by a parent or abandoned outside or worse, defanged/destinged.
5. Red eared slider - These turtles are adorable as babies and they're inexpensive... but don't be fooled. They get very large and need a lot of care. Firstly they need a very large tank for their adult life (upwards of 75 gallons) and enjoy heated water as well as a basking spot and area to get out of the water. They also require intense UVB when young for proper shell formation and cuddle bone to chew on for proper bone formation. They need a filter to keep their water from becoming stagnant as well, which is another costly sum of money with cartridges and what not. They also don't do well with tank mates like fish or smaller turtles, they often end up eating them even. All in all, not a beginner pet, regardless of how cheap or cute they are in the petshop.