Neither medicine nor treatment is limited by species. Reptiles can suffer from all sorts of disorders common to other animals. A short list of culprits includes cancer, bladder stones, goiters, acid base imbalances, and metabolic/kidney/liver diseases (there are many more). Prognosis obviously depends on a number of different factors, but all of the above can be treated. The most common health problems in reptiles are unfortunately related to improper husbandry and are easily preventable.
With your budget, I would recommend visiting the vet to obtain a diagnosis so you know what you are dealing with. It is quite possible that your gecko still has a bacterial or parasitical infection that you treated improperly. Panacur does not kill all parasites, and not all reptile parasites are easily visualized or even in the feces. Baytril can actually CAUSE gastrointestinal problems. Although it is a good broad spectrum antibiotic, it does not kill all bacteria, does not reach all infection locations in high enough concentrations to kill bacteria, and will not kill viruses.
With your budget, I would recommend visiting the vet to obtain a diagnosis so you know what you are dealing with. It is quite possible that your gecko still has a bacterial or parasitical infection that you treated improperly. Panacur does not kill all parasites, and not all reptile parasites are easily visualized or even in the feces. Baytril can actually CAUSE gastrointestinal problems. Although it is a good broad spectrum antibiotic, it does not kill all bacteria, does not reach all infection locations in high enough concentrations to kill bacteria, and will not kill viruses.