An adult should eat mostly salad. Offer a big salad (maybe the size of a closed fist) every day but give more if he wants it. Try to offer as much variety as you can. I like to offer 2-3 items from this list
http://www.beautifuldragons.com/Nutrition.html and rotate based on what looks fresh at the store or farmers market. After a while you will discover favorites and those tend to go into the rotation more often (Squash, collards, and green beans here). The salads are nutritious on their own and need no supplementation. Just keep them fresh.
Bugs are good to offer once or twice per week. I like to rotate these too but roaches are a good staple. It's especially nice to have a roach colony during the winter when shipping live bugs is much tougher (pricier). I like to rotate in silkworms and hornworms and black soldier fly larvae when I can get them. I offer them by hand as a treat between meals sometimes or just as a meal themselves. Dust the bugs with a calcium supplement or an all in one like Repashy Calcium Plus. Light even coat at each meal will do.
Keep in mind that with a rescue he may not be used to this routine so it can take quite a bit of time to get him transitioned over to this. What I outlined is more of an ideal/goal. Notice this is the opposite of what you do with your 3 month old. They transition to this between about 12-18 months in most cases (when their growth slows). Since your new buddy was neglected, focus on offering water at first. Give him salad and see how he does with it. Monitor his weight closely and keep a log so you can see how he is progressing. If he is eating nothing but
drinking, try offering drops of baby food on his nose (green beans, squash, sweet potato). This all depends on the condition he arrives in. I can help you with critical care if needed but hopefully he arrives in reasonably good shape and digs into some salad and drinks some water.
