I mainly feed Yoshi crix. I buy about 50 to 60 at a time and keep them in a cricket keeper. I give the crix Fluker's Calcium Fortifed Cricket Quencher(for a water source) and T-Rex Calcium Plus Food For Crickets(for food) before I dump them in the cricket keeper I sprinkle a little calcium on the bottom of the keeper. The crickets are high in calcium so they are good for Yoshi. I'm not sure if your geckos have a calcium source but if they dont you can place just a small lid of calcium in the cage and they will lick it to maintain their own calcium level (It's very important) As for the mealworms, I only feed Yoshi these everyonce in a while, however I have heard of many people using them souly. I like to vary his food options, it keeps him happy and gives him a varity of different nutrition. To gutload mealworms heres some info.:
Container : The container should be deep enough so that with the substrate added, the mealworms can not climb out. At least 3" deep or more is suitable. A lid on the container will help keep unwanted insects and other animals out, but should allow air flow to prevent molding.
Substrate : You can use oat bran, wheat germ, oatmeal, layena (non-medicated), etc. Make the substrate about 1/4" to 1/2" deep. The deeper the substrate is, the harder it can be to find the mealworms, so use your best judgment when deciding how deep you want to make it. As they eat the substrate, their fecal matter will create a layer of fine particles at the bottom of the container. You can also add finely chopped monkey chow, kitten food, or dog food into the substrate. Some will also add skimmed milk powder or dry milk powder, but I am uncertain of the actual benefits.
Moisture Source : You can use a slice of apple or carrot, piece of potato, cricket gels, or make your own MOISTURE MUNCHIES. The moisture source should be provided on the top of the substrate. Be cautious that the moisture source does not produce mold and that there is enough ventilation in the container. A dish of water is not suitable.
Hope this helps you.