hes probably scared of your huge fingers in his face.
#1 get a basking, try for low to mid 70s on one side, and low 80s on the other. a cold reptile, isnt going to eat. a reptile with a basking, that can self regulate its body temperature and metabolism, is going to eat more, grow more, etc.
#2, it is not going to eat in front of you. expect that a crested of that size, will probably eat 15-20 apropriately sized crickets a week.
- feed it twice a week [like monday and thursday],
toss in like... 5-8 crickets, into the cage, and leave it alone, walk away, and turn out the lights. after 2 days after a feeding, if you still see crickets in there, kill them and wait 3 more days, then offer less the next time [like 3-5]. if in 2 days all the crickets are gone, feed the same ammount, they do NOT need to eat EVERY DAY, they can eat twice a week is fine, dont feed them more often then every other day.
when feeding fruit mash/diet/puree/baby food, dip the cresteds face in the mash, then let it run away, put the dish in the cage, and the crested will find it.
try meal worms, not "super worms". cenchria not zoophoba.
crested geckos, like all rhacodactylus species, and most geckos, are nocturnal, and will not eat in front of you. because they are active, when it is pitch black, and you are probably asleep.
most reptiles, do best, when you leave them alone. being handled, prodded, picked up, things shoved in their face and bright lights flashed at them or on when its "nighttime" is just going to succeed in stressing the animal out, which, ironicly, leads to them not eating.
plants are usually where arboreal geckos "hang out" so that isnt something i would worry about.
and rule of thumb with geckos, if you dont already know this, is the cricket length should be no greater then the width of the geckos eyes.
ps. young crested geckos, dont show much interest in fruit/mash/puree/baby food/ diet, untill they are much older, that doesnt mean they dont eat it, it doesnt mean you should stop offering it, i make sure that mine always have fruit available, and just restrict and control the ammount of crickets are fed. you may not notice a dent, but they probably are eating it.
and when looking for "skinny" on a crested gecko, you want to pay attention to the hip bones, if the bones protrude or you can see the spine really well, sometimes, the most common problem with "skinny" looking geckos, is just that they are totally dehydrated.