As k107 stated, you get what you pay for.
There's no question that the most important items in your vaping setup are your batteries and charger. Buy cheap poor quality batteries and a cheap poor quality charger and you'll end up buying them more frequently when their performance wanes, or
worse. Put out the money at the beginning for a quality charger and batteries, and you'll save money and be safer in the long run. That Trustfire charger is notorius for taking twice as long to charge batteries than higher quality chargers.
Statistically, most battery incidents happen while batteries are being charged. This is when batteries are most vulnerable to go into thermal runaway.
A lower quality charger will be more likely to have inferior wiring and microcircuits. Inferior wiring, inferior circuit boards, and inferior workmanship can lead to potential short circuits resulting in fire and flames. There's a reason why they are less expensive. Again, you usually get what you pay for.
Many vendors throw in cheap batteries and a charger in a starter kit to save themselves money. They are not necessarily interested in your personal safety, but YOU should be.
If your family car needs new brakes, are you going to risk your family's safety by taking your car to the shady auto mechanic who offers you the cheapest brakes he can find? Or will you take your car to a reputable dealer who will put quality brakes on the car and give you a warranty for a safer product? The analogy is the same here. Why risk your family or home on a potentially unsafe charger?
General consensus is that chargers made by Pila, Xtar, Nitecore, and Efest are the best chargers for external rechargeable batteries used in e-cigs. I recommend purchasing your batteries and charger from a reputable vendor like RTD Vapor. So-called "smart chargers" or intelligent chargers have advanced technology and features which make them safer than the cheaper chargers without this feature.
